Motion Test

Result

Motion Test - 3

Score
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out of -
Rank
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TIME Taken - -

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Weekly Quiz Competition

Question 1
1 / -0

Velocity of a body is defined as

A
rate of change of its position

B
change of its position only

C
rate of change of its direction

D
rate of change of its position in a definite direction

Solution

Velocity of a body is defined as the rate of change of its position in a definite direction. As velocity is a vector quantity, so its magnitude and direction both will be considered.
Question 2
1 / -0

Two trains take 3 seconds to pass one another when going in opposite directions, but only 2.5 seconds if speed of one is increased by 50%. The time that one train would take to pass the other when going in the same direction at the original speed is

A
10 sec

B
12 sec

C
15 sec

D
18 sec

Solution

Let the speed of 1^st train be v.
Let the speed of 2^nd train be u.

Let their combined length (distance) be d.
When going in opposite directions with original speeds,

=> (v+u) = d/3
=> d= 3v + 3u .......... Eq (1)

When speed of one train is increased by 50 %, v = 1.5v
(1.5v+u)=d/2.5

d = 3.75v + 2.5 u............Eq (2)
Eq (2) - Eq (1)
0.75v - 0.5u = 0

1.5v = u
Time = Distance/Speed
When going in same direction, time= d/(u - v)

Since d = 3 v + 3 u = 3v + 3 x 1.5 v= 7.5 v,
u - v= 0.5v
Time = 7.5v/0.5v = 15 seconds