Question:

A ball is projected horizontally with a velocity of $5 \,m/s$ from the top of a building $19.6\, m$ high. How long will the ball take of hit the ground ?

Updated On: Jan 12, 2024
  • $\sqrt{2}\,s$
  • $2\, s$
  • $\sqrt{3}\,s$
  • $3\, s$
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The Correct Option is B

Solution and Explanation

The time taken to hit the ground is given by


$T=\sqrt{\frac{2 H}{g}}$
$=\sqrt{\frac{2 \times 19.6}{9.8}}=2 \,s$
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Concepts Used:

Motion in a Plane

It is a vector quantity. A vector quantity is a quantity having both magnitude and direction. Speed is a scalar quantity and it is a quantity having a magnitude only. Motion in a plane is also known as motion in two dimensions. 

Equations of Plane Motion

The equations of motion in a straight line are:

v=u+at

s=ut+½ at2

v2-u2=2as

Where,

  • v = final velocity of the particle
  • u = initial velocity of the particle
  • s = displacement of the particle
  • a = acceleration of the particle
  • t = the time interval in which the particle is in consideration