A block of $$1$$ kg is released from the top of a smooth curve $$\mathrm{AB},$$ and then it encounters a rough surface $$\mathrm{BC},$$ coming to rest at $$\mathrm{C}.$$ The work done by friction is:
(take $$g=10$$ m/s2)

1. $$25$$ J
2. $$50$$ J
3. $$-25$$ J
4. $$-50$$ J

Subtopic: Â Work Energy Theorem |
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The work done by all the forces (external and internal) on a system equals the change in:

 1 total energy 2 kinetic energy 3 potential energy 4 none of these
Subtopic: Â Work Energy Theorem |
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A bullet from a gun is fired on a rectangular wooden block with velocity $$u$$. When bullet travels $$24$$ cm through the block along its length horizontally, velocity of bullet becomes $$u/3$$. Then it further penetrates into the block in the same direction before coming to rest exactly at the other end of the block. The total length of the block is:
1. $$30$$ cm
2. $$27$$ cm
3. $$24$$ cm
4. $$28$$ cm
Subtopic: Â Work Energy Theorem |
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NEET - 2023
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A body of mass $$1$$ kg is thrown upwards with a velocity $$20$$ ms-1. It momentarily comes to rest after attaining a height of $$18$$ m. How much energy is lost due to air friction?
(Take $$g=10$$ ms-2)
1. $$20$$ J
2. $$30$$ J
3. $$40$$ J
4. $$10$$ J

Subtopic: Â Work Energy Theorem |
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AIPMT - 2009
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In a ballistics demonstration, a police officer fires a bullet of mass $$50.0$$ g with speed $$200$$ m/s on soft plywood of thickness $$2.00$$ cm. The bullet emerges with only $$\text{10%}$$ of its initial kinetic energy. The emergent speed of the bullet is:
1. $$0$$
2. $$53.2$$ m/s
3. $$63.2$$ m/s
4. $$6.32$$ m/s

Subtopic: Â Work Energy Theorem |
Â 66%
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