Question

A particle starts from rest, accelerates at 2 m/s² for 10s and then goes for constant speed for 30s and then decelerates at 4 m/s² till it stops. What is the distance travelled by it

• A. 750 m
• B. 800 m
• C. 700 m
• D. 850 m

Answer 1

Answer: (A)

750 m

Answer 2

Velocity acquired by body in 10sec

$v = 0 + 2 \times 10 = 20 ⥂ m/s$

and distance travelled by it in 10 sec

$S_{1} = \frac{1}{2} \times 2 \times (10)^{2} = 100\mspace{6mu} m$

then it moves with constant velocity (20 m/s) for $30\mspace{6mu}\sec$

$\mspace{6mu} S_{2} = 20 \times 30 = 600\mspace{6mu} m$

After that due to retardation $(4m/s^{2})$ it stops

$S_{3} = \frac{v^{2}}{2a} = \frac{(20)^{2}}{2 \times 4} = 50m$

Total distance travelled $S_{1} + S_{2} + S_{3} = 750m$