Question

An object of mass $40kg$ is raised to a height of $5m$ above ground. If the object is allowed to fall down find its kinetic energy when it is half-way down.

• A. 1960 J
• B. 980 J
• C. 990 J
• D. 1000 J

Answer 1

Answer: (B)

980 J

Gravitational Potential energy, $W=mgh$

$h=$ vertical displacement $=5m$

$m=$ Mass of object $=40Kg$

$g=$ Acceleration due to gravity $=9.8m{s}^{-2}$

$Kinetic$ $Energy$ = $Loss$ $in$ $PE$= $40\times 5\times 9.8=1960J$

For half way down$=\frac{1960}{2}=980J$

At this point i.e. half way object has an equal amount of potential and kinetic energy.