Question

A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 m/s², with what velocity will it strike the ground?
1. 30 m/s
2. 35 m/s
3. 20 m/s
4. 43 m/s

Answer 1

Correct Answer - Option 3 : 20 m/s

The correct answer is 20 m/s

• Given, the initial velocity of the ball (u) = 0 (since it began at the rest position).
• Distance traveled by the ball (s) = 20 m
• Acceleration (a) = 10 m/s²

As we know:

⇒  v² = u² + 2as

Putting values:

• v²= 0 + 2 x (10m/s²) × (20 m) 
• v² = 400 m²/s²
• Therefore, v = 20 m/s, when the ball strikes the ground.

• There are three equations of motion that can be used to derive components such as displacement(s), velocity (initial and final), time(t), and acceleration(a).
• The following are the three equations of motion:
  • First Equation of Motion: v = u + at
  • Second Equation of Motion: s = ut + 1/2(at2)
  • Third Equation of Motion: v2 = u2 + 2as