Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 11

# Car Moving at 40 Km/Hr is to Be Stopped by Applying Brakes in the Next 4 M. If the Car Weighs 2000 Kg, What Average Force Must Be Applied - Physics

Sum

car moving at 40 km/hr is to be stopped by applying brakes in the next 4 m. If the car weighs 2000 kg, what average force must be applied to stop it?

#### Solution

Given:
Initial speed of the car, u = 40 km/hr
$= \frac{4000}{3600} = 11 . 11 m/s$
Final speed of the car, v = 0
Mass of the car, m = 2000 kg
Distance to be travelled by the car before coming to rest, s = 4m
Acceleration,
$a = \frac{v^2 - u^2}{2s}$
$\Rightarrow a = \frac{0^2 - \left( 11 . 11 \right)^2}{2 \times 4} = \frac{- 123 . 43}{8} = - 15 . 42 m/ s^2$
∴ Average force to be applied to stop the car, F = ma
⇒ F = 2000 × 15.42 ≈ 3.1 × 104 N

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#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 5 Newton's Laws of Motion
Q 2 | Page 79