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CGP Physics > Section 1-Forces And Motion P1 > Flashcards

Section 1-Forces And Motion P1 Flashcards

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1
Q

What are speed and velocity measured in?

A

m/s

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2
Q

Define speed:

A

Speed is just how fast you’re going with no regard to the direction.

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3
Q

Define velocity:

A

Velocity however must also have the direction specified. (It’s how fast and it also has a direction)

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4
Q

Can an object travel at the same speed but change its velocity?

A

Yes, this happens when an object is changing direction whilst staying at the same speed

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5
Q

What’s the equation linking time taken, distance moved and average speed?

A 
Distance moved(m)
Average speed(m/s) = ———————————
                               Time taken
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6
Q

Define Acceleration:

A

Acceleration is how quickly the velocity is changing.

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7
Q

What can a change in velocity be?

A
  • change in speed

- change in direction

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8
Q

What’s the units for acceleration?

A

m/s²

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9
Q

What does ‘suvat’ stand for?

A 
S = displacement(m)
U = initial velocity(m/s)
V = final velocity(m/s)
A = acceleration(m/s²)
T = time(s)
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10
Q

What’s the equation of motion using final velocity, acceleration, initial velocity and time?

A

v = u + at

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11
Q

What’s the equation of motion using initial velocity, acceleration, final velocity and displacement?

A

v² = u² + 2as

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12
Q

What do distance-time graphs show you?

A

How far something has travelled

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13
Q

What does the gradient on a distance-time graph show you?

A

The gradient at any point gives the speed of the object

  • flat sections mean it’s stopped
  • steeper gradient means it’s going faster
  • curves represent acceleration
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14
Q

How do you use a distance-time graph to calculate the speed of the object?

A

Work out the gradient at a given point

gradient = speed

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15
Q

How do you work out the average speed on a distance-time graph?

A

Do the total distance travelled over the time taken to travel that distance

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16
Q

What’s the gradient on a velocity-time graph?

A

Gradient = acceleration

  • therefore the gradient can be negative or positive
  • flat section represent a constant speed
  • curve means changing acceleration
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17
Q

How do you find the speed of an object on a velocity time graph?

A

Just read off the value on the y axis

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18
Q

How do you work out the distance travelled on a velocity-time graph?

A

Distance travelled = the area under the graph

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19
Q

What’s the equation linking change in velocity, time taken and acceleration?

A

change in velocity
Acceleration = —————————
Time taken

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20
Q

Define gravity:

A

Gravity is the force of attraction between all masses

  • gravity attracts all masses (but you only notice it if it’s a really big mass e.g. a planet)
  • anything near a planet or a star is attracted to it very strongly
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21
Q

What are the three effects of gravity?

A
  • on the surface of the planet, it makes all things accelerate towards the ground(10m/s^2 on earth
  • gives everything a weight
  • keeps planets, moons and satellites in their orbit, orbit is the balance between the forward motion of the object and the force of gravity pulling it inwards
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22
Q

Define mass:

What is its units?

A

Mass is just the amount of ‘stuff’ in an object. For any given object this will be the same value anywhere in the universe.
Mass is not a force
Units: kilograms (measured with a mass balance)

23
Q

Define weight:

A

Weight is caused by the pull of gravity.
Weight is a force.
Units: Newtons (measured using a spring balance/newton meter)

24
Q

What is the equation linking mass, gravitational field strength and weight?

A

weight = mass x gravitational field strength

25
Q

What is the gravitational field strength:
On earth?
On the moon?

A 
Earth = 10 N/kg
Moon = 1.6 N/kg
26
Q

What are some examples of forces?

A

Gravity or Weight (straight down)
Reaction Force (perpendicular force to the object)
Electrostatic Force (between two charged objects)
Thrust (push or pull)
Drag or Air Resistance or Friction (slowing)
Lift (e.g. an aeroplane wing)
Tension

27
Q

How do you show forces acting on an object?

A

-draw arrows from the centre and label the force

28
Q

Define Friction:

A

Friction is a force the opposes motion.
-if an object has no force propelling it along, it will always slow down and stop because of friction (unless you are in space)

29
Q

What are the three main ways which friction occurs?

A
  • FRICTION BETWEEN SOLID SURFACES WHICH ARE GRIPPING (static friction)
  • FRICTION BETWEEN SOLID SURFACES MOVING PAST EACH OTHER (sliding friction)
  • RESISTANCE OR DRAG FROM FLUIDS {LIQUIDS or GASES] (in a fluid friction always increases as the speed increases)
30
Q

How can friction between two solids sliding be reduced?

A

-put a lubricant between the surfaces(e.g. oil or grease)

31
Q

How can resistance or drag from fluids be reduced?

A
  • make the object travelling in fluids streamlined (e.g. boat hulls, lorries have deflectors)
  • no roof boxes (they increase drag)
32
Q

Describe how you can use a toy car to investigate the motion of a toy car on a ramp:

A
  • set up a ramp with a runway, and a toy car before a starting line on the ramp with three light gates at different points along the ramp and runway
  • measure the distance between each light gate
  • let the car go down the ramp, when the car goes through the light gates the time is recorded on a computer by data-logging software
  • repeat the experiment and then find the average times and work out the average speed from that
33
Q

What different ways can you investigate motion?

A
  • how mass affects motion
  • how friction affects motion(different materials)
  • how acceleration affects motion
  • how the angle of a slope travelled on can affect motion
  • how different shape and size can affect motion
34
Q

What is Newton’s first law of motion?

A

So long as all forces are balanced on an object, then it will just stay still or else if it is already moving it will just carry on with the same velocity.

35
Q

What is Newton’s second law of motion?

A

If there is an unbalanced force, then an object will accelerate in that direction.

36
Q

What are the five different forms of acceleration?

A 
Starting 
Stopping
Speeding up
Slowing down
Changing direction
37
Q

What is the equation linking mass, acceleration and resultant force?

A

resultant force(N) = mass(kg) x acceleration(m/s²)

38
Q

Define Vector:

A

Has a size and a direction.

39
Q

Define Scalar:

A

Has just a size.

40
Q

What are some examples of Vectors?

A

force, acceleration, velocity, momentum

41
Q

What are some examples of Scalars?

A

mass, temperature, time, length

42
Q

How do you work out Resultant force by combining vectors?

A

Choose one direction to be positive and then take away any force going in the opposite direction from the positive direction force and this gives t=you the resultant force

43
Q

What is terminal velocity?

A
  • when an object starts to fall, it has much more force accelerating it than resistance slowing it down
  • as velocity increase the resistance builds up
  • the resistant force gradually reduces the acceleration until eventually the resistant force equals the accelerating force, this is its terminal velocity where it wont be ale to accelerate anymore
44
Q

What affects the terminal velocity of objects?

A

Their size and shape on earth because of air resistance
-so a human skydiver will travel quicker through the air without a parachute than with a parachute because of air resistance

45
Q

What is Hooke’s Law?

A

Extension is proportional to force/load.

46
Q

Describe a practical which you can do investigate Hooke’s Law with a spring (or metal wire or rubber band):

A
  • set up a weighted stand with a clamp attached, hold the spring in the clamp and attach set masses to the spring
  • measure the length of the spring when no load is applied
  • add one mass at a time and measure the extension length when the spring has come to rest
  • repeat the experiment and then calculate an average value for each weight applied
  • plot your results on a graph of force by weight
47
Q

When does Hooke’s law stop working?

A

There is a limit to the amount of force you can apply for Hooke’s law to stay true.
-on a graph when Hooke’s law is obeyed it is directly proportional but once the elastic limit is reached the graph will start to curve

48
Q

What happens if you go past an objects elastic limit?

A

Once the elastic limit is surpassed the material will be permanently be stretched

49
Q

Can materials return to their original shape after an elastic deformation?

A

Materials can return to their original shape

  • if a material returns to its original shape after being stretched, it displays elastic behaviour
  • metals display elastic behaviour as long as Hooke’s law is obeyed
50
Q

What affects stopping distance?

A

Thinking distance and Braking distance

51
Q

What is stopping distance?

A

Stopping distance = thinking distance + braking distance

52
Q

What are the two main factors which affect thinking distance?

A
  • How fast you are going

- Reaction time(can be affect by tiredness, drugs, alcohol, old age)

53
Q

What are the four main factors which affect braking distance?

A
  • How fast you are going
  • Mass of the vehicle
  • How good the brakes are
  • How good the grip is(can be affected by road surface, weather conditions, tyres)
54
Q

How are you meant to avoid a car accident?

A

Drivers should leave the stopping distance for whatever speed they are travelling at

CGP Physics (16 decks)

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