Question

When a shot-put champion releases a 5.0 kg shot, it is at 1.5 m above the ground and traveling at 10 m/s. It reaches a maximum height of 5 m above the ground. What are the total mechanical energy, kinetic energy and potential energy of the shot at its maximum height?

• A. 325 J, 75 J, 250 J
• B. 450 J, 125 J, 325 J
• C. 300 J, 100 J, 200 J
• D. 350 J, 125 J, 225 J

Answer 1

The correct option is A

325 J, 75 J, 250 J

Mass of shot-put,m=5 kg

Potential energy at height 1.5 m =mgh

$=5\times 10\times 1.5=75J$

Speed at height 1.5m, $\mu =10m{s}^{-1}$

Kinetic energy at this height $=\frac{1}{2}m{v}^2$ $=\frac{1}{2}\times 5\times {10}^2$ =250 J

Mechanical energy at height 1.5m = K.E+P.E =250J +75J =325 J

According to energy conservation, total energy of a body remains constant.

Hence, at maximum height mechanical energy will be same and is equal to 325 J.

Now, potential energy at maximum height (H)

$P.E=mgH=5\times 10\times 5=250J$

Kinetic energy at maximum height =Total energy -Potential energy

$\Rightarrow K.E=325J-250J=75J$

Hence, at maximum height:

Total energy =325 J

Kinetic energy =75 J

Potential energy =250 J