Brainscape's Knowledge GenomeTM

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


See full index

Edexcel Physiscs > Topic 2: Motion and Forces > Flashcards

Topic 2: Motion and Forces Flashcards

1
Q

What is a scalar quantity

A

It has magnitude but no direction

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

What is a vector quantity?

A

A quantity that has both magnitude and direction

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

explain the difference between vector and scalar quantities

A

Scalars are quantities that only have magnitude (or size), while vectors have both magnitude and direction.

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

what type of quantity is distance

A

scalar

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

what type of quantity is displacement

A

vector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what type of quantity is velocity

A

vector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what type of quantity is speed

A

scalar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what type of quantity is acceleration

A

vector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what type of quantity is force

A

vector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what type of quantity is weight

A

vector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what type of quantity is mass

A

scalar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what type of quantity is momentum

A

vector

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

what type of quantity is energy

A

vector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is velocity

A

speed in a given direction

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

triangle formula for speed

A

distance in m
speed in m/s
time in s

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

How to analyse distance-time graphs?

A
  1. The speed of an object can be calculated from finding the gradient of the slope of a distance time graph
  2. If the speed of an object changes (accelerating or decelerating) this is shown as a curved line on a distance-time graph
  3. If the line is a straight horizontal line then the object is stationary
  4. If the object is moving in a straight line but it is not horizontal then it is moving at a constant/steady speed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the formula for acceleration?

A

acceleration = change in velocity / time

change in velocity = final velocity - initial velocity
time in seconds
velocity = m/s
acceleration = (m/s)²

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

What is another formula for acceleration and velocity?

A

v² - u² = 2 × a × x

v = final velocity
u = initial velocity
a - acceleration

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

How to analyse velocity-time graphs?

A

A steep straight line indicates a constant acceleration where the object is speeding up at the same rate and the velocity is increasing. A straight horizontal line indicates that there is a constant velocity
When the graph reaches the x axis or v = 0 then the object is at rest.
The distance traveled by an object can be calculated from the area under a velocity-time graph

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

Describe a range of laboratory methods for determining the speeds of objects

A

When an object moves through a light gate, the light gate records when and how fast that object moved through it. Light gate get rid of human error caused by reaction times.

For finding someone’s walking speed (or similar), you can use markers and a rolling tape measure to measure the distance and a stopwatch to measure the time taken. Speed = d/t

You can record a video of the moving object and look how far it travels in each frame. Speed = distance travelled in 1 frame × frames per second

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

typical walking speed

A

1.4m/s

22
Q

typical running speed

A

3m/s

23
Q

typical cycling speed

A

5.5 m/s

24
Q

typical car speed in residential area

A

13 m/s

25
Q

typcial speed of cars on a motorway

A

31 m/s

26
Q

typical speed of trains

A

55 m/s

27
Q

tyical speed of planes

A

250 m/s

28
Q

typical speed of ferries

A

15 m/s

29
Q

typical speed of wind speed

A

5-20 m/s

30
Q

typical speed of sound in air =

A

340 m/s

31
Q

how to you convert m/s to km/h

A

multiple m/s valvue by 3.6

32
Q

What is the acceleration of g in free fall?
Estimate the magnitudes of everyday accelerations

A

10 m/s^2 on earth
A car accelerating = possibly 15 m/s

33
Q

What is Newton’s first law? What would happen in the following situations:
a. The resultant force on a body is zero
b. The resultant force is not zero

A
  • an object remains in the same state of motion unless a resultant force acts on it.

a) The body is moving at a constant velocity or is at rest
b) The speed and/or direction of the body changes

34
Q

What is Newton’s second law? (Give two equations)

A

force (newton, N) = mass (kg) × acceleration (m/s^2)
F = m × a

force (N) = change in momentum (kg m/s) ÷ time (s)
F = (mv - mu) ÷ t

35
Q

What is weight? Give the equation for weight

A

Weight is the force acting on an object due to gravity
You can think of the force as acting from the centre of mass of an object

weight (N) = mass (kg) × gravitational field
strength (N/kg)
W = m × g

36
Q

Describe how weight is measured

A

Weight is measured using a calibrated spring balance (or newton meter)

37
Q

Describe the relationship between the weight of a body and the gravitational field strength

A

There is a positive correlation between the weight and gravitational field strength of a body

The weight of an object changes with location because gravitational field strength varies with location (it’s stronger the closer you are to the mass causing the field / more massive objects create stronger fields)

38
Q

Recall the Core Practical: Investigate the relationship between force, mass and acceleration by varying the masses added to trolleys

A
  1. Measure the mass of the trolley, the unit masses and the hanging hook. Measure the length of the piece of card which will interrupt the light gate beams. Set up your apparatus, but don’t attach the string to the trolley.
  2. Adjust the height of the ramp until the trolley just starts to move
  3. Mark a line on the ramp just before the first light gate - this is to make sure the trolley travels the same distance every time. The light gate will record the initial speed of the trolley as it begins to move.
  4. Attach the trolley to the hanging mass by the string. Hold the trolley still at the start line, and then let go of it so that it starts to roll down the slope.
  5. Each light gate will record the time when the trolley passes through it and the speed of the trolley at that time.

The acceleration of the trolley can then be found using acceleration = change in speed ÷ time, with the following values:
- the initial speed of the trolley as it passes through the first light gate (roughly 0 m/s)
- the final speed of the trolley, which equals the speed of the trolley through the second light gate
- the time it takes the trolley to travel between the two light gates

  • By changing the height of the ramp so that the trolley just begins to move, it means that any other forces that are applied (like the force due to gravity caused by the hanging mass) will be the main cause of the trolley accelerating as it travels down the ramp. The size of this acceleration depends on the mass of the trolley and the size of the accelerating force.
  • To investigate the effect of the trolley’s mass: add masses one at a time to the trolley. Keep the mass on the hook constant (so the accelerating force is constant - where the force is equal to the mass on hook × accelerating due to gravity). Repeat steps 2-5 of the experiment each time.
  • To investigate the effect of the accelerating force: start with all the masses loaded onto the trolley and transfer the masses to the hook one at a time. Again, repeat steps 2-5 each time you move a mass. (You transfer the masses because you need to keep the mass of the whole system the same. This is because the accelerating force causes BOTH the trolley and the hanging masses to accelerate).
39
Q

Does an object moving in a circular orbit at a constant speed have a changing velocity? Why?

A

Yes, because it is constantly changing direction, and velocity includes both speed and direction. Since the velocity is constantly changing, this means the object is accelerating. This means there must be a resultant force acting on it.

40
Q

How does an object stay in motion in a circle?

A

There is a resultant force called the centripetal force acting towards the centre of the circle.

41
Q

What is inertial mass?
Define inertial mass as an equation

A

Inertial mass is a measure of how difficult it is to change the velocity of an object

Inertial mass (kg) = force (N) ÷ acceleration (m/s)
m = F ÷ a

42
Q

Recall and apply Newton’s third law both to equilibrium situations and to collision interactions and relate it to the conservation of momentum in collisions

A

Reaction forces are equal and opposite.
Some objects are accelerated more than the other because of differences in mass (a = F ÷ m)

momentum is conserved because the momentum of two objects going in opposite directions will cancel out, since momentum is a measurement of mass times velocity, and velocity is a vector

43
Q

What is momentum?
What is the equation for momentum?

A

momentum (kg m/s) = mass (kg) × velocity (m/s)
p = m × v

44
Q

Describe examples of momentum in collisions

A

A 1,500kg car, travelling at 25 m/s, crashed into the back of a parked car. The parked car has a mass of 1,000 kg. The two cars lock together and continue moving in the same direction as the original moving car.
To calculate the velocity that the two cars move with, first, you find the total momentum before the collision.
p = m × v = 1,500 × 25 = 37,500 kg m/s
new mass of joined cars = 2,500 kg
v = p ÷ M = 37,500 ÷ 2,500 = 15 m/s

45
Q

Explain methods of measuring human reaction times and recall typical results

A

One way is to use a computer-based test (clicking the mouse when the screen changes colour)

Another is the ruler drop test:
1. Sit with your arm resting on a table. Get someone else to hold a ruler so it hangs between your thumb and forefinger, lined up with zero. You may need a third person to be at eye level with the ruler to check it’s lined up.
2. Without warning, the person holding it drops it. The person has to catch the ruler as quickly as possible.
3. The measurement on the ruler at the point where it was caught is how far the ruler dropped in the time it took the person to react. The longer the distance, the longer the reaction time.
4. You can calculate how long the ruler was falling for (reaction time) using the motion equation.
5. Repeat and find an average, keep it fair

A typical reaction time is 0.2-0.6 s, but reaction times in a real situation are longer, e.g. an alert driver will have a reaction time of ~1 s

46
Q

What makes up stopping distance?

A

Stopping distance = thinking distance + braking distance (might be used in an equation)

47
Q

Explain some factors that affect the stopping distance of a vehicle

A
  • the mass of the vehicle
  • the speed of the vehicle
  • the driver’s reaction time
  • the state of the vehicle’s brakes
  • the state of the road
  • the amount of friction between the tyre and the road surface
48
Q

Describe the factors affecting a driver’s reaction time

A

Possible answers:
Tiredness
Alcohol
Drugs
Distractions

49
Q

Explain the dangers caused by large decelerations and estimate the forces involved in typical situations on a public road

A

Large decelerations can cause serious injuries. This is because a large deceleration requires a large force (f=ma)

Safety features in vehicles are designed to increase collision times, which reduces the force, and so reduces the risk of injury e.g. seat belts stretch, air bags slow you down, crumple zones crumple up easily.

Some average vehicle masses:
Car = ~1,500kg or ~1,000kg if easier to use
Single decker bus = ~10,000kg
A loaded lorry = ~30,000kg

A car crashes from 15 m/s.
The car stops in ~1s
the deceleration of the car is (0-15) ÷ 1 = -15 m/s^2
the resultant force acting on the car = 1500 × -15 = -22500 N

50
Q

Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds

A

speed = thinking distance + stopping distance
30 mph or 13 m/s = 9m + 14m = 23m (6 car lengths)
50 mph or 22 m/s = 15m + 38m = 53m (13 cars)
70 mph or 31 m/s = 21m + 75m = 96m (24 cars)

As speed increases, thinking distance increases at the same rate (d = st)

However, speed and braking distance have a squared relationship - if speed doubles, braking distance quadruples, etc

51
Q

Carry out calculations on work done to show the dependence of braking distance for a vehicle on initial velocity squared (work done to bring a vehicle to rest equals its initial kinetic energy)

A

Energy in the car’s kinetic energy store = work done by the brakes
1/2 × mass (kg) × velocity^2 (m/s) = braking force (N) × braking distance (m)
1/2 × m × v^2 = F × d

Edexcel Physiscs (14 decks)

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