Work and Energy Test

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Work and Energy Test - 41

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Weekly Quiz Competition

Question 1
1 / -0

A father holds his child on his shoulders during a parade. The father does no work during the parade because:

A
No force acts on the child

B
The momentum of the child is constant

C
The potential energy of the child is varying

D
The child's kinetic energy is constant

E
The child's distance from the ground remains the same

Solution

We know , work is given by ,
$$W=fd \ cos\theta$$
In the given example, father exerts force on child in upward direction and his displacement is in forward direction , therefore angle between force and displacement is $$90^{o}$$ due to this work done is zero. Also there is no upward or downward displacement of child is taking place as work done is zero. Hence child's distance from the ground remains the same.
Question 2
1 / -0

Calculate the work done by the person to push a box with a force of $$20 N$$ over a distance of $$8.0 m$$ in the direction of the force?

A
$$1.6 J$$

B
$$16 J$$

C
$$160 J$$

D
$$1600 J$$

E
$$16000 J$$

Solution

Work done $$(W)$$
$$W = F\times S$$
$$F$$; applied force
$$S$$; displacement
Given :
$$F = 20N$$
$$S = 8.0$$ m
$$\Rightarrow W = 20 \times 8.0$$
$$\Rightarrow W = 160\ J$$
Question 3
1 / -0

Identify the wrong statement about work.

A
It is the scalar product of force and displacement

B
It is a vector that is always in the same direction as the force.

C
It is measured in joules.

D
It has the same units as energy.

Solution

Work done by a force is given by dot product of force and displacement $$W = F.S =F S$$ $$cos\theta$$
Work done is a scalar quantity.
It is measured in joules and thus has the same units as energy.
Hence statement given in option B is wrong.
Question 4
1 / -0

How much work does a person do in pushing a box with a force of 10 N over a distance of 8.0 m in the direction of the force?

A
0.8 J

B
8.0 J

C
80 J

D
800 J

E
8000 J

Solution

The work done$$(W)$$ by a force-
$$W = \text{force} \times \text{displacement}$$
$$F = 10\ N$$
$$\text{dispalcement} = 8\ m$$
$$\Rightarrow W = 10 \times 8$$
$$\Rightarrow W = 80\ J$$
Question 5
1 / -0

Which of the following is NOT a unit of energy?

A
Watt

B
eV

C
Kilowatt hour

D
Joule

E
Calorie

Solution

Hint: Energy and work have same units.
Explanation :-
$$\bullet$$ Joule, Calorie ,Kilowatt hour and eV are the units of energy while ‘watt’ is the units of power
$$\bullet$$ $$P=\frac{w}{ t} =\frac {joule}{time } =Watt$$
$$\bullet$$ $$ watt \times$$ unit of time is equal to unit of energy ,so Kilowatt hour is unit of energy
$$\textbf{Hence option A correct}$$
Question 6
1 / -0

Identify the best definition of energy?

A
anything that has mass and takes up space

B
distance moved in a period of time

C
ability to do work

D
mode of opperation

E
moment of an object with application of force

Solution

Energy is defined as the ability to do work and its SI unit is Joule.
Question 7
1 / -0

Person $$A$$ stands on the right side of a cart, while Person $$B$$ stands on the left side. The cart is initially at rest. Person $$A$$ pushes on the cart with a force of $$22.0 N$$, and Person $$B$$ pushes on the cart with a force of $$33.0 N$$.
The cart, with no other forces acting on it, starts to move and rolls through a distance of $$2.0 m$$ while both people continue to push with their respective forces.
How much work was done on the cart by Person $$B$$?

A
$$-44.0 J$$

B
$$+22.0 J$$

C
$$+44.0 J$$

D
$$+66.0 J$$

E
None of the above

Solution

Force exerted by person B $$F_B = 33.0$$ N
Displacement of the box in the direction of $$F_B$$ $$S = 2.0$$ m
$$\therefore$$ Work done by person B $$W_B = F_B\times S = 33.0 \times 2.0 = + 66.0$$ J
Question 8
1 / -0

Define one watt:

A
one joule per second

B
one second per joule

C
ten joules per second

D
voltage divided by current

E
resistance multiplied by voltage

Solution

Watt is a SI unit of power which is defined as the energy per unit time i.e $$P =\dfrac{E}{t}$$
Hence one watt is defined as one joule of energy used in one second.
$$\therefore$$ $$W = \dfrac{J}{s}$$
Question 9
1 / -0

A block of mass 10 kg is pulled by a constant horizontal force of 19 N and it is displaced by 15 m across the floor. Calculate the work done.

A
1.3 J

B
30 J

C
285 J

D
5586 J

E
1J

Solution

Given : Force $$F =19 N$$
Displacement $$S= 15$$ m
Work done by a force is $$W= F S $$
$$\therefore$$ $$W = 19 \times 15 = 285$$ $$J$$
Question 10
1 / -0

How much work does a person do in pushing a box with a force of $$20\ N$$ over a distance of $$8.0\ m$$ in the direction of the force?

A
$$1.6\ J$$

B
$$16\ J$$

C
$$160\ J$$

D
$$1600\ J$$

E
$$16000\ J$$

Solution

Given,
Force applied, $$F = 20\ N$$
Displacement, $$d=+8.0\ m$$ (in the direction of the force)

Work done, $$W$$
$$W=F\times d$$
$$W=20\times 8$$
$$W=160\ J$$

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Re-Attempt Weekly Quiz Competition

Work and Energy Test - 41

Result

Work and Energy Test - 41

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SHARING IS CARING

Question 1

No force acts on the child

The momentum of the child is constant

The potential energy of the child is varying

The child's kinetic energy is constant

The child's distance from the ground remains the same

Solution

Question 2

$$1.6 J$$

$$16 J$$

$$160 J$$

$$1600 J$$

$$16000 J$$

Solution

Question 3

It is the scalar product of force and displacement

It is a vector that is always in the same direction as the force.

It is measured in joules.

It has the same units as energy.

Solution

Question 4

0.8 J

8.0 J

80 J

800 J

8000 J

Solution

Question 5

Watt

eV

Kilowatt hour

Joule

Calorie

Solution

Question 6

anything that has mass and takes up space

distance moved in a period of time

ability to do work

mode of opperation

moment of an object with application of force

Solution

Question 7

$$-44.0 J$$

$$+22.0 J$$

$$+44.0 J$$

$$+66.0 J$$

None of the above

Solution

Question 8

one joule per second

one second per joule

ten joules per second

voltage divided by current

resistance multiplied by voltage

Solution

Question 9

1.3 J

30 J

285 J

5586 J

1J

Solution

Question 10

$$1.6\ J$$

$$16\ J$$

$$160\ J$$

$$1600\ J$$

$$16000\ J$$

Solution

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