Question

A car is decelerating at -2m/s² for five minutes. If initial velocity is 72 km/h then find its final velocity

Answer 1

Answer on Question #47470, Physics, Mechanics | Kinematics | Dynamics

A car is decelerating at $-2\mathrm{m/s}^2$ for five minutes. If initial velocity is $72~\mathrm{km/h}$ then find its final velocity

Solution:

Given:

$$a = -2~\mathrm{m/s}^2,$$ $$v_i = 72~\mathrm{km/h} = 20~\mathrm{m/s},$$ $$t = 5~\mathrm{min} = 300~\mathrm{s},$$ $$v_f = ?$$

The kinematic equation that describes an object's motion is:

$$a = \frac{v_f - v_i}{t}$$

Thus,

$$v_f = v_i + a t$$ $$v_f = 20 - 2 \cdot 300 = -580$$

Thus, car stops.

Answer: Final velocity is $0~\mathrm{km/h}$.