Question:medium
A body of mass 10 kg is moving with a speed of 4 m/s. It is brought to rest by a force in 5 seconds. Calculate the work done by the force.
A body of mass 10 kg is moving with a speed of 4 m/s. It is brought to rest by a force in 5 seconds. Calculate the work done by the force.
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The work-energy theorem relates the net work done to the change in kinetic energy. Make sure to account for both the initial and final velocities when calculating work.
Updated On: Feb 19, 2026
- 40 J
60 J
80 J
- 100 J
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The Correct Option is C
Solution and Explanation
The work-energy theorem states that work done equals the change in kinetic energy:
\[
W = \Delta K = \frac{1}{2} m v_{\text{initial}}^2 - \frac{1}{2} m v_{\text{final}}^2
\]
Given:
- \( m = 10 \, \text{kg} \) (mass)
- \( v_{\text{initial}} = 4 \, \text{m/s} \) (initial velocity)
- \( v_{\text{final}} = 0 \, \text{m/s} \) (final velocity, as the body stops).
Calculate the work done:
\[
W = \frac{1}{2} \times 10 \times (4^2 - 0^2)
\]
\[
W = 5 \times 16 = 80 \, \text{J}
\]
The work performed by the force is \( 80 \, \text{J} \).
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