Question

A car moving with a speed of 25 $m{s}^{-1}$ takes a U-turn in 5 seconds, without changing its speed. The average acceleration during these 5 seconds is

• A. 5 $m{s}^{-1}$
• B. 10 $m{s}^{-1}$
• C. 2.5 $m{s}^{-1}$
• D. 7.5 $m{s}^{-1}$

Answer 1

The correct option is B 10 $m{s}^{-1}$

Velocity is vector quantity so direction matters.

$v_i=25m/s,v_f=-25m/s.$

$\Delta v=(-25)-25=-50m/s$

Average acceleration $=\frac{\Delta v}{\Delta t}=\frac{50}{5}=10m{s}^{-2}.$