Work and Energy Test

Result

Work and Energy Test - 37

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Weekly Quiz Competition

Question 1
1 / -0

.............. is said to be done only when the force applied on a body makes the body to move.

A
Work

B
Momentum

C
Retardation

D
None of these

Solution

Work is said to be done when the force applied to a body makes the body move. By definition 'Work = Force x Displacement.
Question 2
1 / -0

A body is moved in a direction opposite to the direction of force acting on it. So:

A
work is done by the force

B
work is done against the force

C
no work is done

D
an infinite amount of work is done

Solution

When displacement is in a direction opposite to the direction of force acting, work is said to be done against the force applied.
Option B
Question 3
1 / -0

The CGS unit of energy is :

A
Dyne

B
Erg

C
Centimetre

D
Pascal

Solution

CGS unit of energy is $$Dyne-cm$$ which is also known as $$erg$$.
Question 4
1 / -0

Which of the following does not have potential energy ?

A
An inflated balloon

B
Water in a flowing river

C
A fruit on the tree

D
A spinning top

Solution

Potential energy is the energy that is stored in an object due to its position above the ground surface and when the object is in motion then it has kinetic energy. Water in a flowing river has kinetic energy.
Question 5
1 / -0

From the following statements find the one that is NOT correct :

A
A flying bird has both potential and kinetic energy

B
A ball rolling on the ground has kinetic energy but no mechanical energy

C
A stretched rubber band has potential energy.

D
Chemical energy can be converted into electrical energy

Solution

The energy of an object by virtue of its motion is known as potential energy.
The energy possessed by a body due to its change in position or shape is called potential energy. For example, A stretched rubber band.
The sum of kinetic energy and potential energy of an object is its total mechanical energy.
A flying bird has both potential and kinetic energy.
A ball rolling on the ground has kinetic energy Therefore, it also has mechanical energy.
Chemical energy can be converted into electrical energy. For example, a battery.
Question 6
1 / -0

In which of the following cases, is a work being done?

A
A boy pushing a wall

B
A coolie walking with a load of 10 kg on his head

C
A girl is climbing up the staircase

D
A student is holding a book in hand

Solution

A) For a boy pushing a wall, there is no displacement of the wall. So, the work done is zero.
B) For a coolie carrying a load on his head, the force applied by the coolie is against the gravity, i.e., the force is vertically upward. And the displacement of the load is horizontally forward. So, the force and the displacement are perpendiculars. This means the work done is zero.
D) Similarly, for a student holding a book in his hands, force is applied against the gravity and the displacement is zero. Hence, the work done is zero.
C) For a girl climbing up the stairs, force is applied against the gravity and the displacement is also upward, i.e., in the direction of the force. So, only here work is done.
Question 7
1 / -0

A boy of mass $$40\ kg$$ runs up a flight of $$50$$ steps, each $$10\ cm$$ high in $$14\ s$$. So, work done by the boy is:

A
$$1960\ J$$

B
$$19.6\ J$$

C
$$980\ J$$

D
$$9.8\ J$$

Solution

Mass of the boy, $$m = 40\ kg$$
Number of steps = $$50$$
Height of each step = $$10\ cm$$
Force on the boy due to gravity, $$F=mg=40\times{9.8}N=392\ N$$
While climbing up the steps, the boy does work against gravity.
Displacement in the vertical direction, $$s=(50\times{10})\ cm=500\ cm=5\ m$$
Displacement is in the direction of force applied by the boy against gravity.
So, work done, $$W=F\times{s}=392\times{5}\ J=1960\ J$$
Question 8
1 / -0

A moving cricket ball possesses

A
Kinetic energy

B
Potential energy

C
Chemical energy

D
Sound energy

Solution

A moving cricket ball possesses kinetic energy.
Formula of kinetic energy$$(KE)$$-
$$KE = \dfrac{ 1 }{ 2 }mv^2$$
$$m$$; mass of the ball
$$v$$; speed of the ball
Question 9
1 / -0

Work in terms of power and time

A
$$\text{power} \times \text{time}$$

B
$$\dfrac{\text{power}}{\text{time}}$$

C
$$\text{power}+\text{time}$$

D
None of these

Solution

The power is-
$$Power = \dfrac{Work}{time}$$
$$\Rightarrow work = power \times time$$
Question 10
1 / -0

Work done by a fielder in catching a ball is

A
Zero

B
Positive

C
Negative

D
None of these

Solution

To catch a ball, the fielder has to stop the ball. This means, force is applied against the motion of the ball. So, the fielder applied the force on the ball and the ball moves in the direction opposite to the direction of force till the ball comes to rest, . Thus work is negative.

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Re-Attempt Weekly Quiz Competition

Work and Energy Test - 37

Result

Work and Energy Test - 37

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Rank

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SHARING IS CARING

Question 1

Work

Momentum

Retardation

None of these

Solution

Question 2

work is done by the force

work is done against the force

no work is done

an infinite amount of work is done

Solution

Question 3

Dyne

Erg

Centimetre

Pascal

Solution

Question 4

An inflated balloon

Water in a flowing river

A fruit on the tree

A spinning top

Solution

Question 5

A flying bird has both potential and kinetic energy

A ball rolling on the ground has kinetic energy but no mechanical energy

A stretched rubber band has potential energy.

Chemical energy can be converted into electrical energy

Solution

Question 6

A boy pushing a wall

A coolie walking with a load of 10 kg on his head

A girl is climbing up the staircase

A student is holding a book in hand

Solution

Question 7

$$1960\ J$$

$$19.6\ J$$

$$980\ J$$

$$9.8\ J$$

Solution

Question 8

Kinetic energy

Potential energy

Chemical energy

Sound energy

Solution

Question 9

$$\text{power} \times \text{time}$$

$$\dfrac{\text{power}}{\text{time}}$$

$$\text{power}+\text{time}$$

None of these

Solution

Question 10

Zero

Positive

Negative

None of these

Solution

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