Correct Answer - Option 4 : 120
CONCEPT:
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Kinetic Energy: When a body is in linear motion, it's energy due to motion will be kinetic energy.
Mathematically:
K = 1/2 × m × v2
where K is the kinetic energy of the body, and m is the mass of the body, and v is its velocity.
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Work-Energy Theorem: The net work done on an object is equal to a change in its Kinetic energy.
W = ΔK
W = Kf -Ki
where W is work done, Kf is final kinetic energy and Ki is initial kinetic energy.
CALCULATION:
Given that initial velocity = 4 m/s
final velocity = 8 m/s
mass of body = 5 Kg
so initial kinetic energy Ki = 1/2 × m × v2 = 1/2 × 5 × 42 = 40 J
final kinetic energy Kf = 1/2 × m × (2v)2 = 1/2 × 5 × 82 = 160 J
Net work done W = ΔK = Kf - Ki = 180 - 40 J
W = 120 J
Hence the correct answer is option 4.