A man pushes a wall and fails to displace it. He does:
1. negative work
2. positive but not maximum work
3. no work at all
4. maximum work

Subtopic:  Concept of Work |
87%
From NCERT
PMT - 1992
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A body constrained to move along the $$\mathrm{z}$$-axis of a coordinate system is subjected to constant force given by $$\vec{F}=-\hat{i}+2 \hat{j}+3 \hat{k}$$ where $$\hat{i},\hat{j}$$ and $$\hat{k}$$ are unit vectors along the $$\mathrm{x}$$-axis, $$\mathrm{y}$$-axis and $$\mathrm{z}$$-axis of the system respectively. The work done by this force in moving the body a distance of $$4$$ m along the $$\mathrm{z}$$-axis will be:
1. $$15$$ J
2. $$14$$ J
3. $$13$$ J
4. $$12$$ J

Subtopic:  Concept of Work |
89%
From NCERT
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A block of mass $$m$$ is being lowered by means of a string attached to it. The system moves down with a constant velocity. Then:

1. Work done by gravity on the block is positive.

2. Work done by F (the force of the string) on the block is negative.

3. Work done by gravity is equal in magnitude to that done by the string.

4. All of the above are true.

Subtopic:  Concept of Work |
75%
From NCERT
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Which of the following is not a unit of energy?
1. watt-hour
2. joule
3. eV
4. N/m

Subtopic:  Concept of Work |
74%
From NCERT
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A particle of mass m1 is moving with a velocity v1 and another particle of mass m2 is moving with a velocity v2. Both of them have the same momentum, but their kinetic energies are E1 and E2 respectively. If m1 > m2 then:

1. $\frac{{\mathrm{E}}_{1}}{{\mathrm{E}}_{2}}=\frac{{\mathrm{m}}_{1}}{{\mathrm{m}}_{2}}$

2. ${\mathrm{E}}_{1}>{\mathrm{E}}_{2}$

3. ${\mathrm{E}}_{1}={\mathrm{E}}_{2}$

4. ${\mathrm{E}}_{1}<{\mathrm{E}}_{2}$

Subtopic:  Concept of Work |
71%
From NCERT
AIPMT - 2004
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A rigid body of mass $$\mathrm{m}$$ is moving in a circle of radius $$\mathrm{r}$$ with constant speed $$\mathrm{v}.$$ The force on the body is $\frac{{\mathrm{mv}}^{2}}{\mathrm{r}}$ and is always directed towards the center. The work done by this force in moving the body over half the circumference of the circle will be:
1. $\frac{{\mathrm{mv}}^{2}}{\mathrm{r\pi }}$
2. ${\mathrm{mr}}^{2}\mathrm{\pi }$
3. zero
4. $2{\mathrm{mv}}^{2}\mathrm{\pi }$

Subtopic:  Concept of Work |
73%
From NCERT
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The kinetic energy of a body is increased by 21%. The percentage increase in the magnitude of linear momentum of the body will be:

1.  10%

2.  20%

3.  Zero

4.  11.5%

Subtopic:  Concept of Work |
62%
From NCERT
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A person of mass 'm' ascends the stairs and goes up slowly through a height 'h'.
Then,

1. Work done by gravity is mgh

2. Work done by normal reaction is mgh

3. Work done by normal reaction is zero

4. Work done by gravity is stored as gravitational P.E.

Subtopic:  Concept of Work |
From NCERT
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Mark the correct statement(s):

1. Internal forces cannot increase the kinetic energy of a system.

2. Internal forces may increase the kinetic energy of a system.

3. Work done by kinetic friction is always negative.

4. Both (2) & (3)

Subtopic:  Concept of Work |
From NCERT
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Work done by frictional force during walking of a man is:

1.  Positive

2.  Negative

3.  Zero

4.  Maybe positive or negative

Subtopic:  Concept of Work |
From NCERT
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