A-Level Physics Mechanics 2

Question 1

Two forces of 3 N and 4 N act at right angles to each other. What is the magnitude of the resultant force?

Accepted Answer

5 N

Answer

Using Pythagoras: R = √(3² + 4²) = √(9 + 16) = √25 = 5 N. This is the classic 3-4-5 right triangle.

Question 2

An object moves in a circle at constant speed. In which direction does the centripetal acceleration act?

Accepted Answer

Towards the centre of the circle

Answer

Centripetal acceleration always acts towards the centre of the circular path. It continuously changes the direction of velocity without changing its magnitude, keeping the object moving in a circle.

Question 3

A spring with spring constant k = 200 N/m is compressed by 0.15 m. What is the elastic potential energy stored?

Accepted Answer

2.25 J

Answer

Elastic PE = ½kx² = ½ × 200 × 0.15² = ½ × 200 × 0.0225 = 2.25 J.

Question 4

What is the principle of conservation of momentum?

Accepted Answer

The total momentum of a closed system remains constant provided no external resultant force acts

Answer

The principle states that in a closed system (no external resultant force), total momentum before an event equals total momentum after. This applies to all collisions and explosions.

Question 5

A 0.5 kg ball moving at 6 m/s collides with a stationary 1.5 kg ball. They stick together. What is their velocity after the collision?

Accepted Answer

1.5 m/s

Answer

Using conservation of momentum: (0.5 × 6) + (1.5 × 0) = (0.5 + 1.5) × v. So 3 = 2v, giving v = 1.5 m/s. This is a perfectly inelastic collision.

A-Level Revision Practice Test

A-Level Revision Practice Test

A-Level Physics Mechanics 2