Question

When brakes are applied the velocity of a car changes from ${30ms}^{-1}to{10ms}^{-1}$ in 5 s. The acceleration produced in it is ____ ${ms}^{-2}$.

• A. $4$
• B. $-4$
• C. $20$
• D. $-20$

Answer 1

Answer: (B)

$-4$

Initial speed $u=30m/s$
Final speed $v=10m/s$
Time $t=5s$
Acceleration $a=\frac{v-u}{t}$
$⟹a=\frac{10-30}{5}=-4m/s^2$