A 40 N object is released from a height of 10 m. Just before it hits the ground, its kinetic energy, in joules is: (ignoring air friction)
Correct answer: A. 400 J
- A. 400 J
- B. 3920 J
- C. 2800 J
- D. 4000 J
Explanation
By law of conservation of energy Gain in K.E = Loss in P.E So, the maximum potential energy is equal to the maximum kinetic just before it hits the ground. As W = mg P.E = mgh = W x h = 40 x 10 = 400J So, Kinetic energy = 400J
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About Work and Energy
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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