Question

A car of mass 2000 kg is moving with a velocity of 18 km/h. Work done to stop this car is:

• A. \( 2.5 \times 10^6 \) joules
• B. \( 2.5 \times 10^5 \) joules
• C. \( 2.5 \times 10^4 \) joules
• D. \( 2.5 \times 10^3 \) joules

Hint:

To calculate the work done to stop an object, use the formula for kinetic energy \( K.E. = \frac{1}{2} m v^2 \) and substitute the mass and velocity.

Answer 1

The Correct Option is B

The work done to stop a car is equal to its initial kinetic energy, which is given by: \[ K.E. = \frac{1}{2} m v^2 \] Where: - \( m = 2000 \, \text{kg} \) - \( v = 18 \, \text{km/h} = 5 \, \text{m/s} \) (convert from km/h to m/s) Substituting the values: \[ K.E. = \frac{1}{2} \times 2000 \times 5^2 = 1000 \times 25 = 25000 \, \text{joules} = 2.5 \times 10^5 \, \text{joules} \] Thus, the work done to stop the car is \( 2.5 \times 10^5 \, \text{joules} \).