A-Level Physics Mechanics

Question 1

A ball is thrown vertically upwards with an initial velocity of 20 m/s. Taking g = 9.8 m/s², what is the maximum height reached?

Accepted Answer

20.4 m

Answer

Using v² = u² + 2as where v = 0 at maximum height: 0 = 400 + 2(-9.8)s, so s = 400/19.6 = 20.4 m.

Question 2

Newton's third law states that when object A exerts a force on object B, object B exerts an equal and opposite force on A. Which of the following is a correct Newton's third law pair?

Accepted Answer

The gravitational pull of the Earth on a book and the gravitational pull of the book on the Earth

Answer

Newton's third law pairs must act on different objects, be the same type of force, and be equal in magnitude but opposite in direction. The gravitational attraction between Earth and book satisfies all three conditions.

Question 3

A 2 kg object is accelerated from rest to 10 m/s in 4 seconds. What is the resultant force acting on it?

Accepted Answer

5 N

Answer

Acceleration = (10 - 0)/4 = 2.5 m/s². Using F = ma: F = 2 × 2.5 = 5 N.

Question 4

A projectile is launched horizontally at 15 m/s from a cliff 80 m high. How long does it take to hit the ground? (g = 10 m/s²)

Accepted Answer

4 s

Answer

Vertical motion: s = ut + ½gt² where u (vertical) = 0. So 80 = ½ × 10 × t², giving t² = 16, therefore t = 4 s. Horizontal velocity does not affect the time to fall.

Question 5

What is the moment of a 60 N force applied at 0.8 m from a pivot, at an angle of 30° to the lever arm?

Accepted Answer

24 N m

Answer

Moment = Force × perpendicular distance = F × d × sin(θ) = 60 × 0.8 × sin(30°) = 60 × 0.8 × 0.5 = 24 N m.

A-Level Revision Practice Test

A-Level Revision Practice Test

A-Level Physics Mechanics