Question

a vehicle of mass 120kg is moving with a velocity of 90kmph what fore should be applied on the vehicle to stop it in 5 s

Answer 1

Question #34331

a vehicle of mass 120kg is moving with a velocity of 90kmph what fore should

be applied on the vehicle to stop it in 5 s

Solution

Let:

$$m = 120 \, \text{kg}$$ $$v_0 = 90 \, \text{km/h} = 25 \, \text{m/s}$$ $$t = 5 \, \text{s}$$ $$F = ?$$

At the equally decelerated motion of the vehicle

$v = v_0 - at$ were $a$ is the acceleration due the force $F$

According to the second Newton's law

$$a = \frac{F}{m}$$ $$v = v_0 - \frac{F}{m} t$$

Such as the final velocity is equal to zero

$$v_0 = \frac{F}{m} t$$ $$F = \frac{v_0 m}{t}$$ $$F = \frac{25 \cdot 120}{5} = 600 \, \text{N}$$

Answer: 600 N.