A car weighs 1000 kg. It is moving with a uniform velocity of 72 km/h towards a straight road. The driver suddenly presses the brakes. The car stops in 0.2 s. The retarding force applied on the car to stop it is
- A. 100 N
- B. 1000 N
- C. 10 kN
- D. 100 kN ✓
Correct Answer: D. 100 kN
Explanation
Initial velocity u = 72~km/h = 20~m/s. Final velocity v = 0. Acceleration a = (0 - 20) / 0.2 = -100~m/s^2. Retarding force F = m \times |a| = 1000 \times 100 = 100000~N = 100~kN.
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