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Question: In a shot put event an athlete throws the shot put of mass 10 kg with an initial speed of 1m/s at \(...

In a shot put event an athlete throws the shot put of mass 10 kg with an initial speed of 1m/s at 45∘45 ^ { \circ } from a height 1.51.5m above ground. Assuming air resistance to be negligible and acceleration due to gravity to be 10 m/s2\mathrm { m } / \mathrm { s } ^ { 2 } , the kinetic energy of the shot put when it just reaches the ground will be

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155.0J

Answer

155.0J

Explanation

Solution

Initial KE of the shotput

=12(10 kg)(Im/s2)=5 J= \frac { 1 } { 2 } ( 10 \mathrm {~kg} ) \left( \mathrm { Im } / \mathrm { s } ^ { 2 } \right) = 5 \mathrm {~J}

Initial PE of the shotput at a height 1.5 m above ground =mgh=(10 kg)(10 m/s2)(1.5 m)=150 J= \mathrm { mgh } = ( 10 \mathrm {~kg} ) \left( 10 \mathrm {~m} / \mathrm { s } ^ { 2 } \right) ( 1.5 \mathrm {~m} ) = 150 \mathrm {~J}

Total initial energy of the shotput = 155J

Since air resistance is negligible and final potential of the shotput as it hits the ground (h=0) is zero, kinetic energy of the shotput on hitting the ground =155J