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PHXI06:WORK ENERGY AND POWER

355791 A particle moves from a point $(- 2 \hat{i} + 5 \hat{j})$ to $(4 \hat{j} + 3 \hat{k})$ when a force of $(4 \hat{i} + 3 \hat{j}) N$ is applied. How much work has been done by the force ?

1 8

J

2 11

J

3 5

J

4 2

J

Explanation:

$\vec{S} =$ Displacement $= (4 \hat{j} + 3 \hat{k}) - (- 2 \hat{i} + 5 \hat{j})$
$= 2 \hat{i} - \hat{j} + 3 \hat{k}$
Work $= \vec{F} \cdot \vec{S} = (4 \hat{i} + 3 \hat{j}) \cdot (2 \hat{i} - \hat{j} + 3 \hat{k}) = 5 j$

NEET - 2016

PHXI06:WORK ENERGY AND POWER

355792 A mass $M$ is lowered with the help of a string by a distance $x$ at a constant acceleration $\frac{g}{2}$ . The magnitude of work done by the string will be

1

M g x

2

\frac{1}{2} M g x^{2}

3

\frac{1}{2} M g x

4

M g x^{2}

Explanation:

$M g - T = \frac{M g}{2}$ or $T = \frac{M g}{2}$
supporting img
or magnitude of work done $= T \times x = \frac{M g x}{2}$

PHXI06:WORK ENERGY AND POWER

355793 Assertion :
Work done is greater than zero, if angle between force and displacement is acute or both are in same direction.
Reason :
Work done by friction on a body sliding down an inclined plane is positive.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

supporting img
$W = F S \cos θ$
We know $\cos 0^{\circ} = 1$ ( When $F$ and $S$ are in same direction )
$\cos 90^{\circ} = 0$
$\Rightarrow$ Assertion is correct
The work done by friction on a body sliding down an inclined plane is actually negative, not positive. So option (3) is correct.
supporting img
$F = m g \sin ϕ$
$f = μ m g \cos ϕ$
Here $θ = ∠ \vec{f}, \vec{S}$
$θ = 180^{\circ} (a s \vec{f} a n d \vec{S} a r e a n t i p a r a l l e l)$
$\Rightarrow$ Work done by $f$ is negative
$\Rightarrow$ Reason is incorrect $(\cos 180^{\circ} = - 1)$
So correct option is (3)

PHXI06:WORK ENERGY AND POWER

355794 A man pushes a wall and fails to displace it. He does

1 Negative work

2 Maximum work

3 Positive but not maximum work

4 No work at all

PHXI06:WORK ENERGY AND POWER

355795 Assertion :
No work is done if the displacement is zero.
Reason :
Work done by the force is defined to be the product of component of the force in the direction of the displacement and the magnitude of displacement.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Work done
$W = F d \cos θ$
If displacement is zero, i.e., $d = 0, W = 0$
So option (1) is correct.

PHXI06:WORK ENERGY AND POWER

355791 A particle moves from a point $(- 2 \hat{i} + 5 \hat{j})$ to $(4 \hat{j} + 3 \hat{k})$ when a force of $(4 \hat{i} + 3 \hat{j}) N$ is applied. How much work has been done by the force ?

1 8

J

2 11

J

3 5

J

4 2

J

Explanation:

$\vec{S} =$ Displacement $= (4 \hat{j} + 3 \hat{k}) - (- 2 \hat{i} + 5 \hat{j})$
$= 2 \hat{i} - \hat{j} + 3 \hat{k}$
Work $= \vec{F} \cdot \vec{S} = (4 \hat{i} + 3 \hat{j}) \cdot (2 \hat{i} - \hat{j} + 3 \hat{k}) = 5 j$

NEET - 2016

PHXI06:WORK ENERGY AND POWER

355792 A mass $M$ is lowered with the help of a string by a distance $x$ at a constant acceleration $\frac{g}{2}$ . The magnitude of work done by the string will be

1

M g x

2

\frac{1}{2} M g x^{2}

3

\frac{1}{2} M g x

4

M g x^{2}

Explanation:

$M g - T = \frac{M g}{2}$ or $T = \frac{M g}{2}$
supporting img
or magnitude of work done $= T \times x = \frac{M g x}{2}$

PHXI06:WORK ENERGY AND POWER

355793 Assertion :
Work done is greater than zero, if angle between force and displacement is acute or both are in same direction.
Reason :
Work done by friction on a body sliding down an inclined plane is positive.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

supporting img
$W = F S \cos θ$
We know $\cos 0^{\circ} = 1$ ( When $F$ and $S$ are in same direction )
$\cos 90^{\circ} = 0$
$\Rightarrow$ Assertion is correct
The work done by friction on a body sliding down an inclined plane is actually negative, not positive. So option (3) is correct.
supporting img
$F = m g \sin ϕ$
$f = μ m g \cos ϕ$
Here $θ = ∠ \vec{f}, \vec{S}$
$θ = 180^{\circ} (a s \vec{f} a n d \vec{S} a r e a n t i p a r a l l e l)$
$\Rightarrow$ Work done by $f$ is negative
$\Rightarrow$ Reason is incorrect $(\cos 180^{\circ} = - 1)$
So correct option is (3)

PHXI06:WORK ENERGY AND POWER

355794 A man pushes a wall and fails to displace it. He does

1 Negative work

2 Maximum work

3 Positive but not maximum work

4 No work at all

PHXI06:WORK ENERGY AND POWER

355795 Assertion :
No work is done if the displacement is zero.
Reason :
Work done by the force is defined to be the product of component of the force in the direction of the displacement and the magnitude of displacement.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Work done
$W = F d \cos θ$
If displacement is zero, i.e., $d = 0, W = 0$
So option (1) is correct.

PHXI06:WORK ENERGY AND POWER

355791 A particle moves from a point $(- 2 \hat{i} + 5 \hat{j})$ to $(4 \hat{j} + 3 \hat{k})$ when a force of $(4 \hat{i} + 3 \hat{j}) N$ is applied. How much work has been done by the force ?

1 8

J

2 11

J

3 5

J

4 2

J

Explanation:

$\vec{S} =$ Displacement $= (4 \hat{j} + 3 \hat{k}) - (- 2 \hat{i} + 5 \hat{j})$
$= 2 \hat{i} - \hat{j} + 3 \hat{k}$
Work $= \vec{F} \cdot \vec{S} = (4 \hat{i} + 3 \hat{j}) \cdot (2 \hat{i} - \hat{j} + 3 \hat{k}) = 5 j$

NEET - 2016

PHXI06:WORK ENERGY AND POWER

355792 A mass $M$ is lowered with the help of a string by a distance $x$ at a constant acceleration $\frac{g}{2}$ . The magnitude of work done by the string will be

1

M g x

2

\frac{1}{2} M g x^{2}

3

\frac{1}{2} M g x

4

M g x^{2}

Explanation:

$M g - T = \frac{M g}{2}$ or $T = \frac{M g}{2}$
supporting img
or magnitude of work done $= T \times x = \frac{M g x}{2}$

PHXI06:WORK ENERGY AND POWER

355793 Assertion :
Work done is greater than zero, if angle between force and displacement is acute or both are in same direction.
Reason :
Work done by friction on a body sliding down an inclined plane is positive.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

supporting img
$W = F S \cos θ$
We know $\cos 0^{\circ} = 1$ ( When $F$ and $S$ are in same direction )
$\cos 90^{\circ} = 0$
$\Rightarrow$ Assertion is correct
The work done by friction on a body sliding down an inclined plane is actually negative, not positive. So option (3) is correct.
supporting img
$F = m g \sin ϕ$
$f = μ m g \cos ϕ$
Here $θ = ∠ \vec{f}, \vec{S}$
$θ = 180^{\circ} (a s \vec{f} a n d \vec{S} a r e a n t i p a r a l l e l)$
$\Rightarrow$ Work done by $f$ is negative
$\Rightarrow$ Reason is incorrect $(\cos 180^{\circ} = - 1)$
So correct option is (3)

PHXI06:WORK ENERGY AND POWER

355794 A man pushes a wall and fails to displace it. He does

1 Negative work

2 Maximum work

3 Positive but not maximum work

4 No work at all

PHXI06:WORK ENERGY AND POWER

355795 Assertion :
No work is done if the displacement is zero.
Reason :
Work done by the force is defined to be the product of component of the force in the direction of the displacement and the magnitude of displacement.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Work done
$W = F d \cos θ$
If displacement is zero, i.e., $d = 0, W = 0$
So option (1) is correct.

PHXI06:WORK ENERGY AND POWER

355791 A particle moves from a point $(- 2 \hat{i} + 5 \hat{j})$ to $(4 \hat{j} + 3 \hat{k})$ when a force of $(4 \hat{i} + 3 \hat{j}) N$ is applied. How much work has been done by the force ?

1 8

J

2 11

J

3 5

J

4 2

J

Explanation:

$\vec{S} =$ Displacement $= (4 \hat{j} + 3 \hat{k}) - (- 2 \hat{i} + 5 \hat{j})$
$= 2 \hat{i} - \hat{j} + 3 \hat{k}$
Work $= \vec{F} \cdot \vec{S} = (4 \hat{i} + 3 \hat{j}) \cdot (2 \hat{i} - \hat{j} + 3 \hat{k}) = 5 j$

NEET - 2016

PHXI06:WORK ENERGY AND POWER

355792 A mass $M$ is lowered with the help of a string by a distance $x$ at a constant acceleration $\frac{g}{2}$ . The magnitude of work done by the string will be

1

M g x

2

\frac{1}{2} M g x^{2}

3

\frac{1}{2} M g x

4

M g x^{2}

Explanation:

$M g - T = \frac{M g}{2}$ or $T = \frac{M g}{2}$
supporting img
or magnitude of work done $= T \times x = \frac{M g x}{2}$

PHXI06:WORK ENERGY AND POWER

355793 Assertion :
Work done is greater than zero, if angle between force and displacement is acute or both are in same direction.
Reason :
Work done by friction on a body sliding down an inclined plane is positive.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

supporting img
$W = F S \cos θ$
We know $\cos 0^{\circ} = 1$ ( When $F$ and $S$ are in same direction )
$\cos 90^{\circ} = 0$
$\Rightarrow$ Assertion is correct
The work done by friction on a body sliding down an inclined plane is actually negative, not positive. So option (3) is correct.
supporting img
$F = m g \sin ϕ$
$f = μ m g \cos ϕ$
Here $θ = ∠ \vec{f}, \vec{S}$
$θ = 180^{\circ} (a s \vec{f} a n d \vec{S} a r e a n t i p a r a l l e l)$
$\Rightarrow$ Work done by $f$ is negative
$\Rightarrow$ Reason is incorrect $(\cos 180^{\circ} = - 1)$
So correct option is (3)

PHXI06:WORK ENERGY AND POWER

355794 A man pushes a wall and fails to displace it. He does

1 Negative work

2 Maximum work

3 Positive but not maximum work

4 No work at all

PHXI06:WORK ENERGY AND POWER

355795 Assertion :
No work is done if the displacement is zero.
Reason :
Work done by the force is defined to be the product of component of the force in the direction of the displacement and the magnitude of displacement.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Work done
$W = F d \cos θ$
If displacement is zero, i.e., $d = 0, W = 0$
So option (1) is correct.

PHXI06:WORK ENERGY AND POWER

355791 A particle moves from a point $(- 2 \hat{i} + 5 \hat{j})$ to $(4 \hat{j} + 3 \hat{k})$ when a force of $(4 \hat{i} + 3 \hat{j}) N$ is applied. How much work has been done by the force ?

1 8

J

2 11

J

3 5

J

4 2

J

Explanation:

$\vec{S} =$ Displacement $= (4 \hat{j} + 3 \hat{k}) - (- 2 \hat{i} + 5 \hat{j})$
$= 2 \hat{i} - \hat{j} + 3 \hat{k}$
Work $= \vec{F} \cdot \vec{S} = (4 \hat{i} + 3 \hat{j}) \cdot (2 \hat{i} - \hat{j} + 3 \hat{k}) = 5 j$

NEET - 2016

PHXI06:WORK ENERGY AND POWER

355792 A mass $M$ is lowered with the help of a string by a distance $x$ at a constant acceleration $\frac{g}{2}$ . The magnitude of work done by the string will be

1

M g x

2

\frac{1}{2} M g x^{2}

3

\frac{1}{2} M g x

4

M g x^{2}

Explanation:

$M g - T = \frac{M g}{2}$ or $T = \frac{M g}{2}$
supporting img
or magnitude of work done $= T \times x = \frac{M g x}{2}$

PHXI06:WORK ENERGY AND POWER

355793 Assertion :
Work done is greater than zero, if angle between force and displacement is acute or both are in same direction.
Reason :
Work done by friction on a body sliding down an inclined plane is positive.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

supporting img
$W = F S \cos θ$
We know $\cos 0^{\circ} = 1$ ( When $F$ and $S$ are in same direction )
$\cos 90^{\circ} = 0$
$\Rightarrow$ Assertion is correct
The work done by friction on a body sliding down an inclined plane is actually negative, not positive. So option (3) is correct.
supporting img
$F = m g \sin ϕ$
$f = μ m g \cos ϕ$
Here $θ = ∠ \vec{f}, \vec{S}$
$θ = 180^{\circ} (a s \vec{f} a n d \vec{S} a r e a n t i p a r a l l e l)$
$\Rightarrow$ Work done by $f$ is negative
$\Rightarrow$ Reason is incorrect $(\cos 180^{\circ} = - 1)$
So correct option is (3)

PHXI06:WORK ENERGY AND POWER

355794 A man pushes a wall and fails to displace it. He does

1 Negative work

2 Maximum work

3 Positive but not maximum work

4 No work at all

PHXI06:WORK ENERGY AND POWER

355795 Assertion :
No work is done if the displacement is zero.
Reason :
Work done by the force is defined to be the product of component of the force in the direction of the displacement and the magnitude of displacement.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Work done
$W = F d \cos θ$
If displacement is zero, i.e., $d = 0, W = 0$
So option (1) is correct.