Question

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. 40 J
• B. 80 J
• C. 60 J
• D. 100 J

Hint:

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.

Answer 1

The Correct Option is C

We can use the work-energy theorem, which states that the work done by the force is equal to the change in kinetic energy: \[ W = \Delta K = \frac{1}{2} m v^2_{\text{initial}} - \frac{1}{2} m v^2_{\text{final}} \] Where: - \( m = 10 \, \text{kg} \) is the mass of the body, - \( v_{\text{initial}} = 4 \, \text{m/s} \) is the initial velocity, - \( v_{\text{final}} = 0 \, \text{m/s} \) (since the body comes to rest). Now, calculate the work done: \[ W = \frac{1}{2} \times 10 \times (4^2 - 0^2) \] \[ W = 5 \times 16 = 80 \, \text{J} \] Thus, the work done by the force is \( 80 \, \text{J} \).