Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

gcse physics > Topic 5 - Forces > Flashcards

Topic 5 - Forces Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards GCSE Religious Studies - Eduqas Route A flashcards
1
Q

What is a force?

A

A push or a pull. Its an interaction between at least 2 bodies.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What 3 things can forces change?

A
  • Change the speed of an object
  • Change the direction of an object
  • Change the shape of an object
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How are forces measured and represented?

A

Measured in Newtons (N) and represented with arrows.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a contact force?

A

When the two bodies physically touch.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are 9 examples of contact forces?

A
  • Normal force/ Reaction Force
  • Friction
  • Air resistance/ Drag
  • Water resistance
  • Tension
  • Spring force
  • Thrust
  • Upthrust/ Buoyancy
  • Lift
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is normal force/reaction force? (3)

A
  • Exists when 2 bodies are touching.
  • It is the force that stops objects passing through each other.
  • Acts at 90 degrees to the surface of contact.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is friction? (4)

A
  • Exists when 2 bodies are touching and moving relative to each other.
  • It’s the force that resists the motion of the object.
  • It acts parallel to the surface of contact and opposes the direction of motion/intended direction of motion.
  • An object at rest on a slope must have friction acting up on it => friction acts up the slope.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is air resistance/drag? (5)

A
  • Type of friction force where it only exists when objects are moving through air.
  • It is caused by the collision of air particles with the body in motion.
  • It opposes motion.
  • Higher speeds = higher air resistance
  • Larger cross sectional area = larger air resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is water resistance? (2)

A
  • Similar to air resistance, but water molecules instead of air molecules.
  • An object travelling through water always experiences water resistance.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is tension? (4)

A
  • Tension is the force acting when a material is stretched.
  • It is always there when a rope, wire, or spring is attached to a body.
  • Always a pull force, as ropes can never be pushed.
  • It acts away from the body it is attached to and along the rope.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is spring force? (2)

A
  • A sprint always wants to restore to its original shape.
  • If a spring is being pulled right, then spring force is acting left and vice versa.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is thrust?

A

Forward force of an object that has an engine, or one that is launched.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is upthrust/buoyancy? (2)

A
  • All objects that float in a fluid, e.g, rubber duck, balloon, etc.
  • Acts upwards => away from fluid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is lift?

A

The force that holds objects with wings up, e.g, planes, butterflies etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a non-contact force?

A

Force that acts at a distance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are 5 examples of non-contact forces?

A
  • Gravitational force/ Weight
  • Electrostatic force
  • Magnetic force
  • Strong force
  • Weak force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is gravitational force/ weight/

A

Force of attraction between objects that have mass (acts towards centre of earth).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is electrostatic force?

A

Force between objects that have a charge.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is magnetic force?

A

Force between objects that have a magnetic field, like a magnet.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is strong force?

A

Force that binds neutrons and protons together in the nucleus of an atom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is weak force?

A

Linked to radioactive decay of protons and neutrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a free body diagram?

A

A diagram representing all the forces acting on an object, with proportionate arrows and labels of newtons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the resultant force and what does it allow us to do?

A
  • The sum of all forces acting on a body is called the resultant force.
  • It allows us to figure out the motion of a body.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What must you do when calculating resultant force?

A

We need to take the direction of any forces acting when we find the total.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What do forces in the same and opposite directions do in relation to resultant force?

A
  • Same direction, add up
  • Opposite direction, cancel out/ balance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

When is the resultant force balanced and unbalanced?

A
  • When resultant force = 0 they are balanced
  • When it doesn’t = 0, they are unbalanced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is mass?

A

Amount of matter in a substance, doesn’t change no matter where in the universe you are. Measured in kg.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is gravitational field strength measured in?

A

N/Kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How is weight measured?

A

Weight is measured using a calibrated spring-balance (a newtonmeter).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Where does the weight of an object act?

A

The weight of an object may be considered to act at a single point referred to as the object’s ‘centre of mass’.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How are weight and mass proportional?

A

The weight of an object and the mass of an object are directly proportional.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the equation to calculate weight?

A

W = mg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What does the value of gravitational field strength depend on?

A
  • Mass of the planet/satellite
  • Distance to the centre of mass of the planet/satellite
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the gravitational field strength on earth?

A

9.8 N/Kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the gravitational filed strength on the moon?

A

1.6 N/Kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Look at flow diagram for balanced forces on phone.

A

Rate based on how well you know it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Look at flow diagram for unbalanced forces on phone.

A

Rate based on how well you know it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

How can you find gravitational filed strength when given weight and mass?

A

g = W/m

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

How can you find gravitational filed strength when given 2 objects with the same radius but different mass, and the value of g for one of them?

A

gB = gA x number of times B is more massive than A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

How can you find gravitational filed strength when given g at the surface, and need to find g at a distance away from the surface? Use e.g, of the surface having 24 N/Kg and needing to find 4 times away from this

A

g = 1/4(2) of 24 = 1.5 N/Kg

Inverse square law

41
Q

How can you find gravitational filed strength when both mass and radius change compared to a known planet?

A

g = (gA x number of times B is more massive than A) / (radius of B compared to A) squared

42
Q

Why do we feel heavy?

A

The feeling of being heavy/ having weight is due to the normal force => the push of the ground on you.

43
Q

Why do you feel weightless in space?

A

The lack of normal force in space gives the sensation of being weightless.

44
Q

What is weightlessness sometimes called and why is this wrong?

A

Objects that are experiencing weightlessness are said to be in zero-g, but g is not 0. Zero g is equivalent to no normal force.

45
Q

What does it mean if something is in free fall?

A

When something is in orbit, the only force acting is the gravitational force. When this happens, we say it’s in free fall.

46
Q

Do all objects fall at the same rate when there is no air resistance?

A

All objects fall at the same rate (same distance in same time) when there is no air resistance. How massive the object is has no influence on how quickly it falls.

47
Q

How does air resistance affect how fast something falls?

A

In the presence of air resistance, the resultant force acting on objects changes, which affects how fas they fall.

48
Q

What is static equilibrium?

A

When forces are balanced but the object is at rest, so it stays at rest.

49
Q

What is dynamic equilibrium?

A

When forces are balanced but the object is already moving, so the object carries on moving in the same direction at the same speed.

50
Q

How does a parachutist fall? (6 steps)

A
  1. Speed increasing rapidly downwards as there’s no air resistance.
  2. Speed increases still, but not as rapidly due to air resistance.
  3. Reached terminal velocity, so falling down at a constant speed => dynamic equilibrium.
  4. Parachute comes out, so speed iOS decreasing but they are still falling down.
  5. Reached terminal velocity again, but its slower than before.
  6. Falls to a complete stop, because normal force is bigger than weight when they hit the ground.
51
Q

What is the rate of acceleration for a parachutist on earth?

A
  • g = 9.8 N/Kg so travelling at 9.8 m/s per second
  • means they’re gaining an extra 9.8 m/s every second
  • 1 second = 9.8 m/s
    2 seconds = 19.6 m/s
    3 second = 28.4 m/s
    etc.
  • air resistance can/will affect these numbers in some way
52
Q

What is the resultant force acting on an object falling at terminal velocity?

A

0N

53
Q

Why do objects falling through air eventually reach a terminal velocity?

A

The air resistance acting on a falling object increases as its speed increases. So as falling objects accelerate, the air resistance increases until it is equal to the objects weight. At this point the resultant force on the object is 0, so it is no longer accelerating and travels at a steady speed (its terminal velocity).

54
Q

Why does a parachutists velocity decrease after opening the parachute if they had already reached their terminal velocity?

A

Before the parachute is opened, the weight of the skydiver acting downward equals the air resistance travelling upwards (because of terminal velocity). Opening the parachute increases the area of the skydiver, so the air resistance acting upwards on the skydiver increases whilst their weight remains the same. This causes the air resistance to be larger than the weight, so the velocity of the skydiver will decrease.

55
Q

What are the variables of the required practical involving springs and extensions?

A
  • Independent variable = Force, F
  • Dependent variable = Extension, e
  • Control variable = Spring constant, k
56
Q

What is the 8 step method for Investigating Force & Extension required practical?

A

1.Set up the apparatus as shown in the diagram, initially without any masses hanging from the spring.
2. Align the marker to a value on the ruler, record this initial length of the spring.
3. Add the 100 mass hanger onto the spring.
4. Record the mass (in kg) and position (in cm) from the ruler now that the spring has extended
5. Add another 100 g to the mass hanger.
6. Record the new mass and position from the ruler now that the spring has extended further.
7. Repeat this process until all masses have been added
8. The masses are then removed and the entire process repeated again, until it has been carried out a total of three times, and an average length is calculated

57
Q

Look at picture on phone of labelled diagram for Investigating Force & Extension required practical.

A

Rate based on how well you know it.

58
Q

What 2 conclusions can be made from the Hooke’s law experiment?

A
  1. The larger the force applied to the spring, the larger the extension of the spring is.
  2. The applied force is directly proportional to the extension (LBF is a straight line through the origin).
59
Q

What is Hooke’s Law?

A

The force applied to a spring is directly proportional to the extension of a spring.

60
Q

What equation can be derived from Hooke’s law?

A

F = Ke

F is applied force in N
K is spring constant in N/cm
e is extension in cm or m

61
Q

What is a spring constant?

A

a measure of the stiffness of a spring

62
Q

How do you set up a force extension graph?

A

Force on the y-axis, and extension on the x so the gradient represents the spring constant.
If the axes are warped, the gradient is no longer spring constant it is the reciprocal => 1/k.

63
Q

What is the limit of proportionality in relation to springs and graphs?

A

Beyond this value of force, the spring no longer follows Hooke’s law. However, when the load is removed, the spring still returns to its original length.

64
Q

What is the elastic limit in relation to springs and graphs?

A

The point beyond which if a larger force were applied, the spring no longer goes back to its original length. The spring becomes permanently deformed.

65
Q

If you have a spring with an extension of 2 cm and a force applied of 1N, what happens to the spring constant when you put them in a series?

A
  • Original
  • F = Ke
  • K = F/e = 1/2 = 0.5 N/cm
  • Series
  • e doubles so becomes 4
  • K = F/e = 1/4 = 0.25 N/cm
  • K halves
66
Q

If you have a spring with an extension of 2cm and a force applied of 40N, what happens to the spring constant when you put 2 springs in parallel?

A
  • Original
  • K = F/e = 40/2 = 20 N/cm
  • Parallel
  • e halves so becomes 1
  • K = F/e = 40/1 = 40 N/cm
  • Spring constant doubles
67
Q

Does a force that stretches or compresses a spring do work? How is energy stored?

A

A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring. Provided the spring is not inelastically deformed, the work done on the spring and the elastic potential energy stored are equal.

68
Q

What is static friction?

A

The force that needs to be overcome to get an object moving, is called static friction.

69
Q

What is kinetic/dynamic friction?

A

The force that needs to be overcome to keep an object, that is already moving, in motion is called kinetic/dynamic friction.

70
Q

In what 2 ways is friction caused?

A
  • Rougher surfaces have ridges and bumps which catch on each other.
  • All materials are made up of tiny particles, called molecules, and these have a tendency to stick to each other when materials are pressed together.
71
Q

What does the size of the fictional force depend on? (2)

A
  • The type of surfaces in contact
  • How hard the surfaces are pressed together
72
Q

Which is usually larger static or kinetic/dynamic friction and why?

A

The size of the static friction between two surfaces is generally larger than the kinetic/dynamic friction between them. This is because it is easier to keep an object in motion once it’s already moving than to begin its movement in the first place.

73
Q

What are the factors affecting friction (class practical conclusions)? (3)

A
  • For the same 2 surfaces, the larger the mass of the object, the larger the static friction is.
    The larger the mass is, the larger the weight so the surface areas are pressed together even more, increasing the friction.
    Static friction is directly proportional to the weight of a body.
  • The type of surface the object is in contact with. In our experiment, out of the floor, the carpet and the bench => floor provided most static friction for the same mass.
  • The area of contact between surfaces is not a factor that affects friction.
74
Q

What is fluid friction with examples?

A

Gases and liquids are called fluids. There is fluid friction whenever an object moves through a fluid. Examples include; air resistance and water resistance.

75
Q

What are 2 ways of increasing the top speed of a vehicle?

A
  1. Reducing drag/air resistance. This can be done by altering the shape of a vehicle to make it more streamlined.
  2. Increasing the power of the vehicles engine. This way, the driving force becomes larger and so the drag force on the vehicle will equal the driving force at a higher speed.
76
Q

What are some typical speed values for someone walking, running and cycling?

A
  • walking - 1.5 m/s
  • running - 3 m/s
  • cycling - 6 m/s
77
Q

What are some typical speed values for a car, train and plane??

A
  • car - 25 m/s
  • train - 55 m/s
  • plane - 250 m/s
78
Q

How do you calculate speed?

A
  • speed = sdistance travelled / time
  • V = s/t
  • distance, s, in metres, m
    speed, v, in metres per second, m/s time, t, in seconds, s
79
Q

In what two ways can you calculate average speed?

A
  • V(avg) = total distance / total time
  • V(avg) = u + V / 2
    initial speed / velocity = u
    final speed / velocity = V
80
Q

How do you calculate acceleration?

A
  • acceleration = change in speed / time taken
  • a = V - u / t
  • a = change in V / change in t
  • acceleration, s, in metres per second squared, m/s(2)
    speed, v, in metres per second, m/s time, t, in seconds, s
    OR
  • (final velocity) squared - (initial velocity) squared = 2 x acceleration x distance
  • V(2) − u(2) = 2 x a x s
81
Q

How do you calculate distance for a constant speed?

A

s = V x t

82
Q

How do you calculate distance for a gradually changing speed?

A

s = V(avg) x t

83
Q

What does Newton’s first law state?

A

If the resultant force acting on an object is zero and:
* the object is stationary, the object remains stationary
* the object is moving, the object continues to move at the same speed and in the same direction. So the object continues to move at the same velocity

84
Q

What did Newton’s experiments prove in relation to his 2nd law (basically what is his 2nd law and how did he come to this conclusion)?

A
  1. Resultant force is directly proportional to acceleration.
  2. The acceleration is inversely proportional to the mass of the body for the same force.
    * This means F is directly proportional to ma , so if we choose the constant to be 1, the equation becomes;
    F = ma
    F is resultant force in N
    m is mass in Kg
    a is acceleration in m/s(2)
85
Q

What are the variables for Newton’s 2nd law required practical?

A
  • Independent variable = force, F
  • Dependent variable = acceleration, a
  • Control variable = Mass, m
86
Q

What is the 5 step method for Newton’s 2nd law required practical?

A
  1. Connect the ticket timer tape to the cart and put it through ticket timer.
  2. Place the cart at the starting line, and place the necessary masses on the cart and at the end of the strong.
  3. Let go of the cart after starting the ticket timer.
  4. Turn the ticket timer off once the masses hit the floor.
  5. Repeat the steps for ‘repeat’ masses, and the different required masses.
87
Q

How do you use the ticket timer in Newton’s 2nd law required practical to calculate acceleration?

A
  • Produces 50 dots in 1 second so the separation between 2 dots in 0.02s. That means 10 dots = 0.2s
  • Measure the length of the first 10 dots and the last 10 dots to calculate the u and v values.
  • With this data you can calculate acceleration
88
Q

How can Newton’s 2nd law required practical method be improved?

A
  • An air track can be used to reduce friction.
  • To improve time measurements, a light gate can be used.
89
Q

When is work done?

A

When a force causes an object to move through a distance work is done on the object. So a force does work on an object when the force causes a displacement of the object.

90
Q

What is the equation for work done?

A
  • Work done = Force x (distance travelled in the direction of the force)
  • W = Fd
  • W = work done in joules, J
    F = Force in newtons, N
    d = distance in metres, m
91
Q

When is one joule of work done?

A

One joule of work is done when a force of one newton causes a displacement of one metre.
1 joule = 1 newton-metre

92
Q

Where is work done applied?

A

Only in the direction of motion

93
Q

How can you calculate work done in the situation of for example a car, if there is both friction and thrust forces?

A

You can subtract the work done by friction, from the work done by the thrust if necessary.

94
Q

What does work done by friction/against friction convert into?

A

It is converted into heat/thermal energy. Any remaining work done is turned into kinetic energy.

95
Q

What happens to the body if all the work done on that body, is equal to the work done by friction?

A

There is no net gain in energy, and the body moves at a constant speed.

96
Q

What happens to a body if the work done by friction is larger than the work done by applied force?

A

The body will slow down, and come to rest if it was already in motion.

97
Q

What happens to the work done on an object, if there is no friction and no change in height (relative to some point)?

A

All the work done would be converted into kinetic energy, so the object would gain speed.

98
Q

What happens when work is done against the gravitational force/weight?

A

The energy is converted into gravitational potential energy. This involves an object changing/gaining height. Lifting an object involves working against the pull of gravity.

99
Q

What happens if there is work done against fictional forces - when there is already gravitational potential energy?

A

Some of the GPE is converted into heat energy (caused by the friction) and any left over energy is converted into kinetic energy.

gcse physics (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions