Topic 10 Forces and Motion

Question 2

What is Newton’s Second Law of Motion?

Answer 2

Force = Mass × Acceleration (F = ma).

Question 3

What is the unit of force?

Answer 3

Newton (N).

Question 4

What is the unit of mass?

Answer 4

Kilograms (kg).

Question 5

What is the unit of acceleration?

Answer 5

Metres per second squared (m/s²).

Question 6

How do you calculate acceleration?

Answer 6

Acceleration = Change in velocity ÷ Time taken.

Question 7

What is deceleration?

Answer 7

Negative acceleration (slowing down).

Question 8

What factors affect acceleration?

Answer 8

Force applied and mass of the object.

Question 9

What is inertial mass?

Answer 9

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

Question 10

How is inertial mass calculated?

Answer 10

Inertial mass = Force ÷ Acceleration.

Question 11

What happens to acceleration if mass increases for the same force?

Answer 11

Acceleration decreases.

Question 12

What happens to acceleration if force increases for the same mass?

Answer 12

Acceleration increases.

Question 13

What is stopping distance?

Answer 13

The total distance a vehicle travels during thinking and braking.

Question 14

What is thinking distance?

Answer 14

Distance travelled during the driver’s reaction time.

Question 15

What is braking distance?

Answer 15

Distance travelled after brakes are applied until vehicle stops.

Question 16

What factors affect thinking distance?

Answer 16

Speed, reaction time (alcohol, drugs, tiredness).

Question 17

What factors affect braking distance?

Answer 17

Speed, road conditions, weather, tyre and brake conditions.

Question 18

What is the equation for stopping distance?

Answer 18

Stopping distance = Thinking distance + Braking distance.

Question 19

What is typical human reaction time?

Answer 19

Between 0.2 – 0.9 seconds.

Question 20

How can reaction time be measured?

Answer 20

Ruler drop test.

Question 21

How does speed affect braking distance?

Answer 21

Braking distance increases with the square of speed.

Question 22

Why are wet or icy roads dangerous for braking?

Answer 22

Less friction means longer braking distances.

Question 23

What is momentum?

Answer 23

Mass × Velocity.

Question 24

What is the unit of momentum?

Answer 24

Kilogram metres per second (kg·m/s).

Question 25

What does the law of conservation of momentum state?

Answer 25

Total momentum before = Total momentum after (in a closed system).

Question 26

What happens in an explosion to momentum?

Answer 26

Momentum is conserved, objects move in opposite directions.

Question 27

How is force related to change in momentum?

Answer 27

Force = Change in momentum ÷ Time.

Question 28

How can you reduce impact force in a collision?

Answer 28

Increase the time over which momentum changes (e.g., crumple zones, seatbelts, airbags).

Question 29

Why do crumple zones reduce injury?

Answer 29

They increase the time taken for the car to stop, reducing the force.

Question 30

How do seat belts protect passengers?

Answer 30

They stretch slightly, increasing stopping time and reducing force.

Question 31

How do airbags reduce injuries?

Answer 31

They spread the force across the body and increase stopping time.

Question 32

How does a helmet reduce injury?

Answer 32

Cushions the impact, increasing time taken to stop the head.

Question 33

How do you calculate change in momentum?

Answer 33

Change in momentum = mass × change in velocity.

Question 34

What is an inelastic collision?

Answer 34

Objects stick together, momentum conserved, but kinetic energy is not.

Question 35

What is an elastic collision?

Answer 35

Momentum and kinetic energy are both conserved.

Question 36

What happens to momentum if two objects collide and move together?

Answer 36

Their combined mass moves with a shared velocity.

Question 37

How does mass affect momentum?

Answer 37

Greater mass = greater momentum (if velocity is constant).

Question 38

How does velocity affect momentum?

Answer 38

Greater velocity = greater momentum (if mass is constant).

Question 39

What happens if resultant force is zero on a moving object?

Answer 39

It continues at constant velocity.

Question 40

How do forces cause a change in momentum?

Answer 40

A resultant force changes the velocity, hence momentum changes.

Question 41

What happens to passengers when a car suddenly stops?

Answer 41

They continue moving forward due to inertia.