A train of $$150\,m$$ length is going towards North direction at a speed of $$10\,m/s.$$ A parrot flies at the speed of $$5\,m/s$$ towards South direction parallel to the railways track. The time taken by the parrot to cross the train is
A.
$$12\,s$$
B.
$$8\,s$$
C.
$$15\,s$$
D.
$$10\,s$$
Answer :
$$10\,s$$
Solution :
Velocity of $$A$$ w.r.t. $$B$$ is given by $${v_{AB}} = {v_A} - {v_B}.$$
Relative velocity of the parrot w.r.t. the train $$ = \left[ {10 - \left( { - 5} \right)} \right]m{s^{ - 1}}$$
$$ = 15\,m{s^{ - 1}}.$$
Time taken by the parrot to cross the train $$ = \frac{{150}}{{15}} = 10\,s$$
Releted MCQ Question on Basic Physics >> Kinematics
Releted Question 1
A river is flowing from west to east at a speed of $$5$$ metres per minute. A man on the south bank of the river, capable of swimming at $$10$$ metres per minute in still water, wants to swim across the river in the shortest time. He should swim in a direction-
A boat which has a speed of $$5 km/hr$$ in still water crosses a river of width $$1 \,km$$ along the shortest possible path in $$15 \,minutes.$$ The velocity of the river water in $$km/hr$$ is-
In $$1.0\,s,$$ a particle goes from point $$A$$ to point $$B,$$ moving in a semicircle of radius $$1.0 \,m$$ (see Figure). The magnitude of the average velocity-
A ball is dropped vertically from a height $$d$$ above the ground. It hits the ground and bounces up vertically to a height $$\frac{d}{2}.$$ Neglecting subsequent motion and air resistance, its velocity $$v$$ varies with the height $$h$$ above the ground as-