Question:

A stone is thrown with an initial speed of 4.9m/s4.9\, m / s from a bridge in vertically upward direction. It falls down in water after 2sec2\, \sec. The height of bridge is

Updated On: Jun 7, 2022
  • 24.7 m
  • 19.8 m
  • 9.8 m
  • 4.9 m
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The Correct Option is C

Solution and Explanation

Here: Initial velocity u=4.9m/su=-4.9\, m / s (-ve is due to vertically upward motion)
Total time t=2sect=2\, \sec
The height of the bridge is given by
s=ut+12gt2s =u t+\frac{1}{2} g t^{2}
=4.9×2+12×9.8×(2)2=-4.9 \times 2+\frac{1}{2} \times 9.8 \times(2)^{2}
=9.8+19.6=9.8m=-9.8+19.6=9.8\, m
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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:

  1. 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.
  2. 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.