Work Energy Theorem: Practice Problem & Solution
A bullet of mass 10g is fired horizontally with a velocity 1000 ms–1 from a rifle situated at a height 50m above the If the bullet reaches the ground with a velocity 500 ms–1, the work done against air resistance on the bullet is : (g = 10 ms–2)
Short Solution (Best for NEET):
To solve this problem, we apply the core principles of Work Energy Theorem. Understanding the underlying formula is key to arriving at the correct answer below:
From Work Energy Theorem,
Total Work Done = Change in Kinetic Energy
Work Done by Gravity + Work Done by Air Resistance = ½m (Vf 2 - Vi 2 )
0.001 × 10×50 + Work done by Air Resistance = ½× 0.001×( 500² - 1000²)
Solving We get, Work Done by Air Resistance = - 3755 J
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