Mechanics

Written by Dr. Hamza Farooq (Physics)

ECAT · Physics · 7 questions

Name: ____________________ Date: ____________

A ball is thrown vertically upward at 20 m/s. What maximum height does it reach? (g = 10 m/s², no air resistance)
- A 40 m
- B 10 m
- C 5 m
- D 20 m
A ball is thrown vertically upward at 20 m/s. How long does it take to reach its highest point? (g = 10 m/s², no air resistance)
- A 0.5 s
- B 2 s
- C 1 s
- D 4 s
A 5 kg block slides down a frictionless incline of 30 degrees. What is its acceleration? (g = 10 m/s²)
- A 10 m/s²
- B 5 m/s²
- C 8.7 m/s²
- D 2.5 m/s²
A force of 10 N acts perpendicular to a spanner at a distance of 0.5 m from the nut. What torque is produced?
- A 20 N m
- B 10 N m
- C 0.05 N m
- D 5 N m
A skater spinning with arms outstretched pulls her arms in. Her angular velocity:
- A Becomes zero
- B Decreases
- C Stays the same
- D Increases
A 2 kg ball moving at 3 m/s collides head-on and elastically with a stationary 2 kg ball. What happens?
- A Both move at 1.5 m/s
- B The first ball stops and the second moves at 3 m/s
- C Both stop
- D The first ball rebounds at 3 m/s
How much energy is stored in a spring of constant 200 N/m stretched by 0.1 m?
- A 20 J
- B 0.1 J
- C 10 J
- D 1 J

Answer key

1. D, 2. B, 3. B, 4. D, 5. D, 6. B, 7. D

Using v² = u² - 2gh with v = 0 gives h = u² / 2g = 400 / 20 = 20 m.
t = u / g = 20 / 10 = 2 s.
The acceleration along a frictionless incline is g sin(theta) = 10 x 0.5 = 5 m/s². The mass does not matter.
Torque = force x perpendicular distance = 10 x 0.5 = 5 N m.
Angular momentum is conserved. Pulling the arms in reduces the moment of inertia, so the angular velocity must rise.
For an elastic collision between equal masses, the velocities are exchanged.
Energy = 1/2 k x² = 0.5 x 200 x 0.01 = 1 J.