A block of mass 2kg is slided on a rough surface at t=0,if its speed is 2m/s. It stops after covering a distance of 20cm because of the friction exerted by the surface on it. Calculate the work done
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There is only one force acting on the block.
The work done on the block of mass 2 kg by the friction force F in stopping it from a velocity of 2 m/s through a displacement S = 20 cm is: W
v² - u² = 2 a S, v = 0 => - u² = 2 a S
=> -1/2 m u² = m a S
=> -1/2 m u² = F S = W
W = - kinetic energy at t = 0
= - 1/2 *2 * 2² = - 4 Joules.
Work done is negative because the block moved against the force. The direction of force and displacement of the block are opposite.
The work done on the block of mass 2 kg by the friction force F in stopping it from a velocity of 2 m/s through a displacement S = 20 cm is: W
v² - u² = 2 a S, v = 0 => - u² = 2 a S
=> -1/2 m u² = m a S
=> -1/2 m u² = F S = W
W = - kinetic energy at t = 0
= - 1/2 *2 * 2² = - 4 Joules.
Work done is negative because the block moved against the force. The direction of force and displacement of the block are opposite.
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