Forces and Motion

Question 1

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

Answer 1

The moon has less mass compared to the earth

Question 2

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

Answer 2

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

Question 3

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

Answer 3

Poor car launch

Friction could slow the car down

Reaction time may cause stopping the stopwatch to be inaccurate

Question 4

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

Answer 4

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

Question 5

Why is the acceleration of a plane not constant even though the engine produces a constant force?

Answer 5

Air resistance acts on the plane causing it to decelerate considering there is a resultant force acting on the aircraft as the speed increases

Question 6

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

Answer 6

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

Question 7

How do you measure extension?

Answer 7

Measure the length of elastic band without the weights using a ruler then measure then measure length with 12N masses. Subtract the two values to obtain extension.

Question 8

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

Answer 8

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

Question 9

How to measure weight

Answer 9

Using a balance

Question 10

Why would an increase in the impact time decrease the risk of injury

Answer 10

A longer impact time reduces the force on the person for the same change of momentum

Question 11

What happens as momentum increases all the time?

Answer 11

As momentum increases, velocity increases

Question 12

SI unit for mass?

Answer 12

Kilograms (Kg)

Question 13

mx –> x

Answer 13

Divide by 1000

Question 14

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

Answer 14

Acceleration is 10

Question 15

How does the graph show that the ball accelerates when it falls?

Answer 15

• Gradient = speed
• Gradient increases as time increases
• Speed increases with time

Question 16

Factors increasing braking distance

Answer 16

• Poor brake quality
• Increased mass of vehicle
• Increased speed of vehicle
• Road may be wet or icy hence, poor road conditions

Question 17

Terminal Velocity questions

Answer 17

• At the start, accelerates as speed increases because the force of weight is greater than air resistance
• as the speed increases, force of air resistance acts on the thing which increases and becomes greater than the force of weight hence, reluctant force decreases therefore causing velocity to decrease and the thing to decelerate
• As the thing falls, force of air resistance becomes equal to weight hence, reaching terminal velocity

Question 18

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

Answer 18

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

Question 19

What does it mean when reluctant force of something increases or decreases in the context of speed

Answer 19

• When speed decreases, reluctant force decreases
• when speed increases, reluctant force increases

Question 20

How might protective gear reduce risk of injury to the person?

Answer 20

• Time of impact increases
• Force on person decreases
• Pressure on person decreases
• For the same change in momentum

Question 21

How to deal with anomalous results?

Answer 21

• Repeat the anomaly

Question 22

Principal of moments? (2 marks)

Answer 22

• For an object to be in equilibrium,
• Total moments clockwise = Total moments anticlockwise

Question 23

Define centre of gravity

Answer 23

• The point where the mass of an object is concentrated