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Separate Science - Physics Paper 2 > Separate Physics - P5 Forces > Flashcards

Separate Physics - P5 Forces Flashcards

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1
Q

What two things does a force arrow show?

A
  1. The length of the arrow shows the size of the force.
  2. The direction of the arrow shows the direction of the force.
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2
Q

Give some examples of non-contact forces

A
  • Gravitational force
  • Electrostatic force
  • Magnetic force
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3
Q

What is a ‘resultant force’?

A

The sum of all forces acting on an object

(the overall force acting on an object)

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4
Q

What equation links force, spring constant and extension?

A

Force = spring constant x extension

F = k e

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5
Q

Give some examples of contact forces

A
  • Friction
  • Air resistance
  • Tension
  • Normal contact force
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6
Q

What are the units for:

a) gravitational field strength
b) weight
c) mass

A

a) N/kg
b) N
c) kg

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7
Q

What is the equation that links work done, force and distance?

A

Work done = force x distance

W = F s

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8
Q

What equation links weight, mass and gravitational field strength?

A

Weight = mass x gravitational field strength

W = m g

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9
Q

Why type of energy is stored in a spring that is stretched or compressed?

A

Elastic potential energy

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10
Q

What happens to the temperature of an object experiencing friction?

A

Temperature increases

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11
Q

What is the name of an object that:

a) will return to its original shape after being deformed
b) will not return to its original shape after being deformed

A

a) elastic
b) inelastic

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12
Q

What is the relationship between force and extension of an elastic object?

A

Directly proportional

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13
Q

What happens to air resistance as speed increases?

A

As speed increases, air resistance increases.

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14
Q

What are typical speed values for someone walking, running and cycling (m/s)?

A
  • Walking 1.5 m/s
  • Running 3 m/s
  • Cycling 6 m/s
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15
Q

What is the speed of sound?

A

340 m/s

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16
Q

How many forces need to to be applied to this spring to stretch or compress it?

A

Two forces (e.g. one at either end)

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17
Q

What equation links acceleration, final velocity, initial velocity and time?

A
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18
Q

What equation links distance travelled, speed and time?

A

Distance travelled = speed x time

s = v t

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19
Q

Why does a falling object reach terminal velocity?

A
  • The resultant force on the object is zero.
  • Forces of weight and air resistance are balanced.
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20
Q

Name the point on the graph labelled ‘X’

A

Limit of proportionality

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21
Q

Describe the motion in the following distance-time graph at points a, b, c and d.

A

a) constant speed
b) stationary
c) accelerating
d) decelerating

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22
Q

If you wanted to investigate how mass affects acceleration, what part of the equipment would you change?

A

The mass of the trolley (by adding more masses to the trolley).

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23
Q

Which part of the equipment measures acceleration?

A

Light gate

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24
Q

If you wanted to investigate how force affects acceleration, what part of the equipment would you change?

A

The force pulling the trolley (by adding more masses to the hook).

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25
Q

What is the equation for Newton’s Second Law that links force, mass and acceleration?

A

Force = mass x acceleration

F = m a

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26
Q

Give three factors that can affect braking distance.

A
  • Road conditions
  • Weather conditions: wet / icy roads
  • Vehicle conditions: condition of brakes / tyre tread depth
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27
Q

What equation links momentum, mass and velocity?

A

Momentum = mass x velocity

p = m v

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28
Q

What happens if a car undergoes a large deceleration?

A

Brakes overheating / loss of control

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29
Q

Describe the motion of a moving car experiencing balanced forces.

A

Keep moving at a constant speed

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30
Q

Describe the motion of a moving car experiencing unbalanced forces.

A

The car will change speed (either accelerate or decelerate)

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31
Q

Describe the motion of a stationary car experiencing balanced forces.

A

The car will remain stationary.

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32
Q

Describe the motion of a stationary car experiencing unbalanced forces.

A

The car will accelerate.

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33
Q

What are typical everyday speeds for cars, trains and planes?

A
  • Car 25 m/s
  • Train 55 m/s
  • Plane 250 m/s
34
Q

What is stopping distance?

A

The sum of the thinking distance and the braking distance

35
Q

What is braking distance?

A

The distance covered during the braking force.

36
Q

What are ‘typical’ reaction times?

A

0.2 s to 0.9 s

37
Q

What is Newton’s Third Law?

A

Whenever two objects interact, the forces they exert on each other are equal in size and opposite in direction.

38
Q

What is thinking distance?

A

The distance covered during the driver’s reaction time.

39
Q

How does speed affect stopping distance?

A

Stopping distance increases with speed.

40
Q

Give three factors that can affect a driver’s reaction time.

A
  • Tiredness
  • Drugs
  • Alcohol
41
Q

What is work done the same as?

A

Energy transferred

42
Q

If your mass on Earth is 50 kg, what would be your mass on the moon?

A

The same, 50 kg.

Your mass does not change.

43
Q

What are the units for:

a) force
b) acceleration
c) weight
d) mass

A

a) N
b) m/s2
c) N (weight is a force)
d) kg

44
Q

Name the forces acting on the book.

A
45
Q

Calculate the resultant force on the box

A

0 N (there is no resultant force)

46
Q

Calculate the resultant force on the box.

A

2N to the left

47
Q

Describe the experiment to investigate how force affects the extension of the spring.

A
  • Measure the starting length of the spring using the ruler.
  • Add one 10 g mass, measure the extension of the spring using the ruler.
  • Repeat 5 times, each time adding one 10 g mass and measuring the extension of the spring.
48
Q

Higher Q. What is inertia?

A

The tendency of objects to continue in their state of rest / uniform motion

49
Q

Higher Q. How can the displacement of an object (the distance travelled) be calculated from a velocity-time graph?

A

The area under a velocity-time graph

50
Q

Higher Q. What is inertial mass?

A

A measure of how difficult it is to change the velocity of an object.

51
Q

Higher Q. How can the motion of an object in a circle be described?

A

Constant speed but changing velocity

52
Q

Separate Q. What equation links force, distance and moment of a force?

A

Moment of a force = force x distance

53
Q

Separate Q. What is a moment?

A

A turning effect of a force

54
Q

Separate Q. What are the SI units for:

a) moment
b) force
c) distance

A

a) newton-metres, Nm
b) newtons, N
c) metres, m

55
Q

Separate Q. In order to calculate the moment of a force, how should distance be calculated in relation to the pivot?

A

Distance should be calculated perpendicular to the pivot.

56
Q

Separate Q. If the first gear is turned clockwise, what direction will the other gears turn in?

A

*arrows show the direction (clockwise or anticlockwise)

57
Q

Separate Q. Explain how a lever makes it easier for us to do ‘work’.

A
  • Levers increase the distance between the pivot and the force applied.
  • You then need to apply less force to achieve the same moment because: moment = force x distance
58
Q

Separate Q. Pressure in a liquid causes a force to be applied to the surfaces of its container. At what angle is the force applied to the surface of the container?

A

Right angles / 90o

59
Q

Separate Q. Explain how different sized gears can be used to change the size of a moment.

A
  • A force transmitted from a smaller gear to a larger one will cause a bigger moment (and vice versa).
  • This is because the distance to the pivot is larger because moment = force x distance.
60
Q

Separate Q. Explain the relationship between speed and stopping distance in this graph.

A
  • Stopping distance is the sum of the thinking distance and braking distance.
  • Thinking distance increases linearly with speed.
  • As speed doubles, braking distance increases 4-fold.
  • Because of this, braking distance (and hence the stopping distance) increases at a greater rate as speed increases.
61
Q

Separate Q. Explain how gears can transmit moments.

A
  • Gears have teeth which interlock with other gears.
  • Rotating one gear will cause the adjacent gear to rotate in the opposite direction.
  • They can transmit the moment of a force from one place to another.
62
Q

Separate Q. If an object is balanced, what is true about the size of the clockwise and anti-clockwise moments?

A

They are equal in size.

63
Q

Separate Q. What two states of matter can be described as a fluid?

A

A liquid or a gas

64
Q

Separate Higher Q. Describe and explain the relationship between the density of a liquid and pressure.

A
  • Density is a measure of the mass of particles per unit volume.
  • The denser a liquid is, the more particles there are.
  • Therefore, with more particles, there are more collisions, so pressure increases as density increases.
65
Q

Separate Q. Describe and explain the relationship between atmospheric pressure and height.

A
  • As the height above Earth increases, atmospheric pressure decreases.
  • This is because as altitude increases, the atmosphere becomes less dense.
  • This means there are fewer particles, resulting in fewer collisions with the Earth’s surface.
  • Also, as altitude increases, there are fewer air particles above, therefore there is a decrease in the weight of particles from above causing a decrease in pressure.
66
Q

Separate Higher Q. If an object floats, what is the relationship between its weight and upthrust?

A

Weight equals upthrust.

67
Q

Separate Higher Q. What happens to an object if it is denser than the fluid it is placed in?

A

It will sink – it weighs more than the equivalent volume of fluid it has displaced

68
Q

Separate Q. What equation links pressure, force and area?

A
69
Q

Separate Higher Q. What two things does pressure in a liquid depend on?

A
  • Depth
  • Density of the liquid
70
Q

Separate Higher Q. Explain why an object in a fluid experiences upthrust.

A
  • Pressure increases with depth.
  • Therefore pressure is greatest at the bottom of the object compared with the top.
  • This creates a resultant force upwards (upthrust).
71
Q

Separate Higher Q. What happens to an object if it is less dense than the fluid it is placed in?

A

It will float – it weighs less than the equivalent volume of fluid it has displaced

72
Q

Separate Q. What is the atmosphere around Earth and how does it change with altitude?

A

A thin layer of air around the Earth which gets less dense with increasing altitude

73
Q

Separate Q. Explain why braking distance increases by 4-fold as speed doubles.

A

When a car stops, its kinetic energy store decreases to 0 J.

Ek = 1/2mv2 means that as the speed of a car doubles, it’s kinetic energy increases 4-fold.

Work done = energy transferred.

So the work done to stop the car increases by 4-fold.

W = Fs means that under a constant braking force, the braking distance will also increase 4-fold.

74
Q

Separate Q. What happens to momentum when a force acts on an object that is moving or able to move?

A

A change in momentum occurs

75
Q

Separate Higher Q. What’s the relationship between upthrust acting on an object and the weight of the fluid displaced by the object?

A

Upthrust is equal to the weight of the fluid displaced by the water.

76
Q

Separate Q. What causes atmospheric pressure?

A

Air molecules colliding with a surface

77
Q

Separate Q. Give examples of safety features used to reduce the rate of change of momentum.

A
  • Air bags
  • Seat belts
  • Gymnasium crash mats
  • Car crumple zones
  • Cycle helmets
  • Cushioned surfaces on playgrounds
78
Q

Separate Q. What are the SI units for:

a) Pressure
b) Force
c) Area

A

a) Pressure is measured in pascals (Pa)
b) Force is measured in newtons (N)
c) Area is measured in metres squared (m2)

79
Q

Separate Higher Q. Describe and explain the relationship between the depth of a liquid and pressure.

A
  • As depth increases, pressure increases.
  • Because, as depth increases, the number of particles above increases.
  • Pressure increases because of the increased weight of particles above.
80
Q

Separate Q. Calculate the velocity of a 2 g bullet that is fired from a 1 kg gun. The gun has a recoil of -0.2 m/s.

*This is just an example, this type of calculation can be applied to any explosion event.

A

Momentum before = 0 kgm/s (because the gun and bullet are stationary).

Momentum of gun after (p = mv):

= 1 kg x -0.2m/s = -0.2 kgm/s

Momentum before = momentum after

Momentum of bullet must be +0.2 kgm/s to make the momentum after = 0 kgm/s (same as before).

v= p/m therefore velocity of bullet = +0.2 kgm/s ➗ 0.002 kg = 100 m/s

81
Q

Separate Q. Explain how safety features (e.g. seat belts, air bags e.t.c) work to reduce injuries to a person.

A
  • They increase the time taken to stop.
  • This decreases the rate of change of momentum.
  • This reduces the force on the person because:
  • F = (m𝝙V)/𝝙t
  • Therefore reducing the injuries to the person.
82
Q

Separate Q. A 50 kg skater is skating from left to right at a velocity of 2 m/s. A 75 kg skater is skating from right to left with a velocity of 1.5 m/s. The two skaters collide and skate away together. Calculate the velocity of the skaters as they move away.

*This is just an example, this type of calculation can be applied to any collision event.

A

*This answer assumes left to right as positive.

Skater 1 momentum: 50 kg x 2 m/s = +100 kgm/s

Skater 2 momentum: 75 kg x 1.5 m/s = -112.5 kgm/s

Momentum before = +100 + -112.5 = -12.5 kg m/s

momentum before = momentum after

Momentum after = -12.5 kg m/s

Combined mass of skaters = 50 + 75 = 125 kg

v= p/m therefore velocity of skaters = -12.5 kgm/s ➗ 125 kg = -0.1 m/s

Separate Science - Physics Paper 2 (4 decks)

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