Question

A rocket is launched upward from the Earth's surface whose velocity-time graph is shown in figure.
The maximum height attained by the rocket is:

• A. $1km$
• B. $10km$
• C. $100km$
• D. $60km$

Answer 1

The correct option is D $60km$

From the graph we can see that its velocity is $increasing$

till $20sec$ then its gets $decreasing$ till $120sec$ after $120sec$ its velocity $changed$ its direction.

so at $t=120sec$ it was at the top most point.

So we just need to calculate the area of triangle $OAB$ for the maximum height. which is $\frac{base\times perpendicular}{2}=\frac{120\times 1000}{2}m=60km$

Option D is correct.