Question:
A $120\, m$ long train is moving towards west with a speed of $10\, m / s$. A bird flying towards east with a speed of $3\, m / s$ crosses the train. The time taken by the bird to cross the train will be :
A $120\, m$ long train is moving towards west with a speed of $10\, m / s$. A bird flying towards east with a speed of $3\, m / s$ crosses the train. The time taken by the bird to cross the train will be :
Updated On: Jul 2, 2022
- 16 sec
- 12 sec
- 10 sec
- 8 sec
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The Correct Option is D
Solution and Explanation
Here : Length of train $l=120\, m$
Speed of train $v_{\text {train }}=10\, m / s$ towards west
Speed of bird $v_{\text {bird }}=5\, m / s$ towards east The relative velocity of bird with respect to the train
$v=v_{\text {train}}+v_{\text {bird }}=10+5=15\, m / s$
Hence, time taken to cross the train is
$=\frac{s}{v}=\frac{120}{15}=8\, \sec$
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Concepts Used:
Motion in a straight line
The motion in a straight line is an object changes its position with respect to its surroundings with time, then it is called in motion. It is a change in the position of an object over time. It is nothing but linear motion.
Types of Linear Motion:
Linear motion is also known as the Rectilinear Motion which are of two types:
- Uniform linear motion with constant velocity or zero acceleration: If a body travels in a straight line by covering an equal amount of distance in an equal interval of time then it is said to have uniform motion.
- Non-Uniform linear motion with variable velocity or non-zero acceleration: Not like the uniform acceleration, the body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time. The rate of change of its velocity changes at different points of time during its movement.