Question 155: Motion in 1D

Question

A car moves from X to Y with a uniform speed v
u
and returns to Y with a uniform speed v
d
. The average speed for this round trip is

Accepted Answer

Let total distance = 2S
Let car take t
1
time to cover first S distance from X to Y,
$ 	herefore $ t
1
= ${S \over {{v_u}}}$
Let car take t
2
time to cover S distance,from Y to X,
$ 	herefore $ t
2
= ${S \over {{v_d}}}$
$ 	herefore $ Average speed = ${{2S} \over {{S \over {{v_u}}} + {S \over {{v_d}}}}}$ = ${{2{v_u}{v_d}} \over {{v_u} + {v_d}}}$

Answer

$\sqrt {{v_u}{v_d}} $

Answer

${{{v_d}{v_u}} \over {{v_d} + {v_u}}}$

Answer

${{{v_u} + {v_d}} \over 2}$

Answer

${{2{v_d}{v_u}} \over {{v_d} + {v_u}}}$

Motion in 1D

A car moves from X to Y with a uniform speed v u and returns to Y with a uniform speed v d . The average speed for this round trip is

Choose the correct answer: