# A stone tied to a string of length L is whirled in a vertical circle with the other end of the string at the centre. At a certain instant of time, the stone is at its lowest position and has a speed u. The magnitude of the change in its velocity as it reaches a position where the string is horizontal is: (1) $\sqrt{{u}^{2}-2gL}$ (2) $\sqrt{2gL}$ (3) $\sqrt{{u}^{2}-gl}$ (4) $\sqrt{2\left({u}^{2}-gL\right)}$

Subtopic:  Work Energy Theorem |
From NCERT
PMT - 2004
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The driver of a car travelling at velocity v suddenly sees a broad wall in front of him at a distance d. He should

(1) Brake sharply

(2) Turn sharply

(3) (1) and (2) both

(4) None of the above

Subtopic:  Concept of Work |
From NCERT
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Which of the following graph depicts spring constant k versus length l of the spring correctly

 (1) (2) (3) (4)
Subtopic:  Elastic Potential Energy |
68%
From NCERT
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Work done by a frictional force is

(1) Negative

(2) Positive

(3) Zero

(4) All of the above

Subtopic:  Concept of Work |
61%
From NCERT
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A block of mass 50 kg slides over a horizontal distance of 1 m. If the coefficient of friction between their surfaces is 0.2, then work done against friction is

(1) 98 J

(2) 72J

(3) 56 J

(4) 34 J

Subtopic:  Concept of Work |
84%
From NCERT
AIIMS - 2000
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A body of mass m is moving in a circle of radius r with a constant speed v. The force on the body is $\frac{m{v}^{2}}{r}$ and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle

(1) $\frac{m{v}^{2}}{\pi {r}^{2}}$

(2) Zero

(3) $\frac{m{v}^{2}}{{r}^{2}}$

(4) $\frac{\pi {r}^{2}}{m{v}^{2}}$

Subtopic:  Concept of Work |
84%
From NCERT
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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 moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joules, the angle which the force makes with the direction of motion of the body is

(1) 0°

(2) 30°

(3) 60°

(4) 90°

Subtopic:  Concept of Work |
87%
From NCERT
PMT - 1999
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A force acts on a 30 gm particle in such a way that the position of the particle as a function of time is given by $x=3t-4{t}^{2}+{t}^{3}$, where x is in metres and t is in seconds. The work done during the first 4 seconds is

(1) 5.28 J

(2) 450 mJ

(3) 490 mJ

(4) 530 mJ

Subtopic:  Work Done by Variable Force |
61%
From NCERT
PMT - 1998
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The minimum work done in pulling up a block of wood weighing $$2$$ kN for a length of $$10$$ m on a smooth plane inclined at an angle of $$15^\circ$$ with the horizontal is (given: $$\mathrm{sin}15^\circ=0.2588)$$:
1. $$4.36$$ kJ
2. $$5.17$$ kJ
3. $$8.91$$ kJ
4. $$9.82$$ kJ

Subtopic:  Work done by constant force |
79%
From NCERT
PMT - 2003
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