C3 - Linear Motion

Question 1

What is a direct force?

Answer 1

A force that is applied through the centre of mass, resulting in linear motion.

Example: A sprinter pushing off the starting blocks.

Question 2

What is Newton’s 1st Law (Inertia)?

Answer 2

An object will remain at rest or in uniform motion unless acted on by an external force.

Example: A football remains stationary until kicked.

Question 3

What is Newton’s 2nd Law (Acceleration)?

Answer 3

The force applied to an object equals its mass x acceleration (F=ma). More force = greater acceleration.

Example: A heavier rugby player needs more force to accelerate than a lighter player.

Question 4

What is Newton’s 3rd Law (Action-Reaction)?

Answer 4

For every action, there is an equal and opposite reaction.

Example: A sprinter pushes against the blocks, and the blocks push back, propelling them forward.

Question 5

What is speed?

Answer 5

The rate of change of distance (measured in m/s). Formula: Speed = Distance ÷ Time.

Example: A runner completing 100m in 10s has a speed of 10 m/s.

Question 6

What is distance?

Answer 6

The total path travelled by an object, measured in metres (m).

Question 7

What is displacement?

Answer 7

The shortest straight-line distance from the start to the finish. It includes direction (a vector quantity).

Question 8

How is velocity different from speed?

Answer 8

Velocity includes direction as well as magnitude. Formula: Velocity = Displacement ÷ Time.

Question 9

What is acceleration?

Answer 9

The rate of change of velocity over time. Formula: (Final Velocity - Initial Velocity) ÷ Time.

Question 10

What is deceleration?

Answer 10

A negative acceleration where velocity decreases over time.

Example: A football slowing down after being kicked.

Question 11

What does a distance-time graph show?

Answer 11

• Gradient = speed.
• A flat line means the object is stationary.
• A steep line shows a fast speed.
• A curved line shows acceleration or deceleration.

Question 12

What does a speed-time graph show?

Answer 12

• Gradient = acceleration.
• A flat line means constant speed.
• A rising line shows acceleration.
• A falling line shows deceleration.

Question 13

What does a velocity-time graph show?

Answer 13

• Similar to a speed-time graph but includes direction.
• Positive velocity = forward motion.
• Negative velocity = backward motion.
• Crossing the x-axis means a change in direction.