Forces and Motion

Question 1

What is the formula for acceleration?

Answer 1

acceleration = change in velocity/time taken

Question 2

What is the formula for final speed?

Answer 2

(𝑓𝑖𝑛𝑎𝑙 𝑠𝑝𝑒𝑒𝑑) 2 = (𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑠𝑝𝑒𝑒𝑑) 2 + (2 × 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 × 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒) 𝑣 2 = 𝑢 2 + 2𝑎

Question 3

what are acceleration’s measuring units?

Answer 3

acceleration is measured in metres per second squared (m/s2)

Question 4

What is the formula for force?

Answer 4

Force = mass of object x acceleration

F = m x a

Question 5

What is the formula for Weight?

Answer 5

Weight = mass x gravitational field strength

W= mg

Question 6

What are some of the factors that increase ‘thinking distance’?

Answer 6

1. Greater speed
2. Slower reaaction time due to alcohol, drugs, etc.

Question 7

How can reaction time be increased?

Answer 7

Reaction time can be increased by caffeine which reduces the thinking distance.

Question 8

What are some factors that increase the ‘stopping distance’ ?

Answer 8

1. Greater speed or mass
2. Poor road conditions(icy,wet) or car conditions(worn tires, worn brake pads)

Question 9

What is Elastic deformation?

Answer 9

Elastic deformation is when a object returns to it’s original shape.

Question 10

What is the formula of moment?

Answer 10

Moment = force x perpendicular distance from the pivot

moment = Fd

Question 11

What is the formula of momentum?

Answer 11

Momentum = mass x velocity

P = mv

Measured in kilogram meters per second (Kgm/s)

Question 12

Why is the gravitational field strength smaller on the moon than on the earth?

Answer 12

The moon has less mass compared to the earth

Question 13

How do you take measurements to find the speed of the car at the bottom of a slope?

Answer 13

1. Place a light gate at the end of the ramp
2. Record the time taken using a stopwatch as the car passes through
3. Measure the distance of the slope using a ruler

Question 14

For the experiment to investigate speed of a car, why might a student get different results?

Answer 14

1. Poor car launch
2. Friction could slow the car down
3. Reaction time may cause stopping the stopwatch to be inaccurate

Question 15

Why must the value of the train be higher than the value calculated?

Answer 15

The train doesn’t travel at a constant speed throughout the journey and could’ve been faster at other stations

Question 16

Why should the airline not use an airplane that has a higher mass and needs a higher speed for landing

Answer 16

Stopping distance is affected by the mass and a faster plane requires a greater distance and as well as does a heavier plane

Question 17

How does the upward acceleration of the balloon change during the first few seconds of the flight of a hot air balloon (3)

Answer 17

The speed increases hence, drag increases which leads to upward acceleration to decrease

Question 18

What does it mean for acceleration if there is presumably no air resistance?

Answer 18

Acceleration is 10

Question 19

In the context of terminal velocity, why do lighter objects reach it faster?

Answer 19

Lighter objects reach terminal velocity faster
due to a smaller drag force being required
therefore, it falls slower

Question 20

How do you measure the scales on a distance/time graph or a velocity/time graph?

Answer 20

• Look at the biggest value in the y-axis
• Look if the figure is nice or not
• ‘nice’ = a number that usually ends with 0, 2, or 5
• Need to use ‘big boxes’

Question 21

What does the gradient of a velocity/time graph represent?

Answer 21

Acceleration

Question 22

What does the gradient of a distance/time graph represent?

Answer 22

Speed/Velocity

Question 23

What does a flat line on a distance/time graph tell us?

Answer 23

A flat line on a distance/time graph tells us that the object is stationary

Question 24

What does a flat line on a velocity/time graph tell us?

Answer 24

A flat line on a velocity/time graph tells us that the object is moving at a constant speed

Question 25

What does a curved line on a distance/time graph tell us?

Answer 25

A curved line in a distance/time graph tells us that the velocity is changing/accelerating

Question 26

What does a curved line on a velocity/time graph tell us?

Answer 26

A curved line in a velocity/time graph tells us that the acceleration is changing

Question 27

How do you calculate the distance traveled in a velocity/time graph?

Answer 27

Find the area under the graph in a velocity/time graph to calculate the distance traveled

Question 28

What does the area under the graph on a distance/time graph represent?

Answer 28

Nothing

Question 29

While the balloon is still accelerating, the pilot controls the balloon by pouring some sand from the bags.

Explain how this affects the upward acceleration of the balloon.
(2)

Answer 29

• Weight decreases
• Acceleration increases

Question 30

Describe what the student should do to test his prediction that the ‘more weight the toy car has, the faster it will roll down the slope’. (5)

Answer 30

• Measure the weight/mass
• Measure the distance of the slope
• Measure the speed by putting light gates at the end of the slope ( and use a stopwatch to calculate the time taken to cover the distances between the light gates)
• Repeat the experiment with an average
• Use the equation - S = d/t

Question 31

Why does the velocity stay at a constant value? (3)

Answer 31

There is a constant velocity which means there is no acceleration/ acceleration = 0 as well as the resultant force, and also the upward force is balanced with the downward force.

Question 32

Explain what effect the cushion of air has on the movement of the glider. (2)

Answer 32

• Speed remains almost constant
• Friction is reduced

Question 33

Explain in terms of forces why the box and parachute fall at constant velocity.

Answer 33

• Weight acts downwards
• drag acts upwards
• Constant velocity = no acceleration
• Resultant force = ma

Question 34

A model car company produces battery powered model cars. At its maximum acceleration, their latest model accelerates from rest to its top speed in 3.5s.

A) While the car is traveling at its top speed, it covers 180 m in 9.0s. Calculate the car’s maximum acceleration.

B) Calculate how fast the car would be moving if it accelerated from rest for 1.5s with its maximum acceleration.

Answer 34

A) V = s/t = 180/9 = 20

A = v-u/t = 20-0/3.5 = 5.71 m/s^2

B) a = v-u/t —> v = (a x t) + u = (5.71 x 1.5) + 0 = 8.57m/s^2

Question 35

The plane deploys a parachute to slow down when it lands. Explain why the parachute slows the plane down.

Answer 35

• Increasing the drag on the plane lowers its speed
• The parachute experiences higher drag compared to the plane, as the parachute is released the drag will increase even more, therefore, slowing the plane down

Question 36

State a difference between the orbit of a moon and the orbit of a planet.

Answer 36

• A moon orbits the planet
• A planet orbits the sun

Question 37

The radius of the Moon’s orbit is 385,000 km.

It takes 27 days for the Moon to complete one orbit,

Calculate the orbital speed of the Moon.

Answer 37

V =(2 x n x 385,000)/ 27 = 2 417 800/27 = 90 000 km/day

Question 38

Describe how she could use this apparatus to find the acceleration of the trolley down the ramp

Answer 38

• Release the trolley so it can roll freely down the ramp and use light gates to record the time at which the trolley passes through them
• The acceleration on the ramp can be found using acceleration = change in velocity/time taken
• The time taken for the trolley to accelerate on the ramp will be the time taken to pass between light gates A and B
• Since the trolley started at rest just before light gate A, its initial speed is 0 m/s and the change in velocity between light gates A and B is equal to its speed between light gates B and C
• To find the trolley’s speed on the runaway, use the time taken for the trolley to pass from light gate B to light gate C and the distance between them
• To calculate the final speed of the trolley average speed = distance moved/time taken

Question 39

Suggest why the ball traveled further on the Moon than it would have done on Earth.

Answer 39

• Gravitational field strength is lower on the moon
• Lack of air resistance on the moon

Question 40

A Tractor ploughing a field accelerates at 2m/s^2 for 10 meters, after which its velocity is 7m/s.

A) calculate the tractor’s velocity before it starts accelerating.

B) As the tractor approaches the end of the field, it turns at a constant speed until it’s facing the opposite direction. State whether the tractor accelerates during this time and explain your answer.

Answer 40

A) v^2 = u^2 + 2 as

—> u^2 = square root = v^2 - 2as = square root 7^2 - (2x2x10)

= 3m/s

B) The tractor does accelerate as it has changed direction as well as
there is a change in velocity.