Question

A car moves with a constant velocity of ${10ms}^{-1}$ for 10 s along a straight road. Then it moves with uniform acceleration of ${2ms}^{-2}$ for $5$ seconds. Find the total displacement at the end of the 15 s of its motion.

• A. $175$ m
• B. $125$ m
• C. $150$ m
• D. $105$ m

Answer 1

The correct option is A $175$ m

For constant velocity :

Constant velocity $u=10m/s$

Time $t=10s$

So, displacement in 10 seconds $S_1=ut=10\times 10=100m$

For accelerated journey :

Initial speed $u=10m/s$

Acceleration $a=2m/s^2$

Time $t=5s$

Displacement in 5 seconds, $S_2=ut+\frac{1}{2}a{t}^2$

$⟹S_2=10\times 5+\frac{1}{2}\times 2\times 5^2=75m$

Total displacement in 15 seconds $S_{total}=100+75=175m$