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Question
Earth revolves around the Sun at 30 km s−1. Calculate the kinetic energy of the Earth. In the previous example, you calculated the potential energy of the Earth. What is the total energy of the Earth in that case? Is the total energy positive? Give reasons.
Solution
Given: V = 30 km s−1
Potential energy = − 49.84 × 1032 J
Mass of earth = 5.9 × 1024
Formula:
Kinetic energy (K.E.) = `1/2"MV"^2`
= `1/2 xx 5.9 xx 10^24 xx 30 xx 30 xx 10^32`
= `1/2 xx 5.9 xx 3 xx 3 xx 10^32`
K.E. = 26.55 × 1032 J
∴ T.E. = K.E. – P.E.
T.E. = 26.55 × 1032 – 49.84 × 1032
T.E. = – 23.29 × 1032 J
Total energy is negative. It implies Earth is bounded with Sun.
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