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: