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Important Questions (1 mark): Work & Energy

25 Questions MCQ Test NCERT Textbooks (Class 6 to Class 12) | Important Questions (1 mark): Work & Energy

Description

Attempt Important Questions (1 mark): Work & Energy | 25 questions in 25 minutes | Mock test for UPSC preparation | Free important questions MCQ to study NCERT Textbooks (Class 6 to Class 12) for UPSC Exam | Download free PDF with solutions

QUESTION: 1

When a light and a heavy body have equal K.E, then which one has a greater momentum?

A.
Light body
B.
Heavy body
C.
Both have equal momentum
D.
Uncertain

Solution:

QUESTION: 2

In SI system, the unit of P.E. is

A.
erg
B.
dyne-cm
C.
J
D.
None of these

Solution: Joule. As potential energy is a form of energy so it's SI unit is also Joule. The gravitational potential energy has the same units as kinetic energy, kg m2 / s2. In fact, all energy has the same units, kg m2 / s2, and is measured using the SI unit is Joule (J).

QUESTION: 3

Kilowatt hour (kWh) represents the unit of

A.
Energy
B.
Impulse
C.
Power
D.
None of these

Solution:

The kilowatt-hour (SI symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy equal to 3600 kilojoules (3.6 megajoules). The kilowatt-hour is commonly used as a billing unit for energy delivered to consumers by electric utilities.

QUESTION: 4

When speed of a motor car increases six times, then kinetic energy increases by

A.
6 times
B.
36 times
C.
12 times
D.
24 times

Solution:

Let initial speed of the car be v m/s and mass be m kg
Using the equation
K.E.= (mv²) / 2
It can be observed that, if we increase the speed (v) by 6 times the kinetic energy will increase by 36 times.

QUESTION: 5

1 kWh equals

A.
36 × 10² Joules
B.
36 × 10⁴ Joules
C.
3.6 × 10⁶ Joules
D.
None of these

Solution:

QUESTION: 6

When speed of the moving object is doubled its

A.
Acceleration is doubled
B.
Momentum becomes four times more
C.
K E. is increased to four times
D.
Potential energy is increased

Solution:

QUESTION: 7

When time taken to complete a given amount of work increases, then

A.
Power increases
B.
Power decreases
C.
Energy increases
D.
Energy decreases

Solution:

QUESTION: 8

When the force applied and the displacement of the body are inclined at 90° with each other, then work done is

A.
Infinite
B.
Maximum
C.
Zero
D.
Unity

Solution:

QUESTION: 9

The KE. of a body in increased most by doubling its

A.
Mass
B.
Weight
C.
Speed
D.
Density

Solution:

QUESTION: 10

If a force F is applied on a body and it move with velocity v, then power will be :-

A.
F x v
B.
F/v²
C.
F/v
D.
F × v²

Solution:

QUESTION: 11

Work done by a centripetal force

A.
Increases by decreasing the radius of the circle
B.
Decreases by increasing the radius of the circle
C.
Increases by increasing the mass of the body
D.
Is always zero

Solution:

QUESTION: 12

Potential energy and kinetic energy are types of

A.
Electrical energy
B.
Magnetic energy
C.
Thermal energy
D.
Mechanical energy

Solution:

Mechanical energy is the energy that is possessed by an object due to its motion or due to its position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position).

QUESTION: 13

Work done in moving a 50 kg block through a horizontal distance of 10 m by applying a force of 100N which makes an angle of 60° with the horizontal is

A.
200 joule
B.
425 joule
C.
500 joule
D.
575 joule

Solution:

We know, work done :-
W = FS cos theta
Here, F = 100 , S = 10 , theta = 60°
So, W = 100 * 10 * cos 60°
W = 500 J

QUESTION: 14

kWh is the unit of

A.
Force
B.
Power
C.
Time
D.
Energy

Solution:

QUESTION: 15

An elevator is designed to lift a load of 1000 kg through 6 floors of a building averaging 3·5 m per floor in 6 sec. Power of the elevator, neglecting other losses, will be

A.
3·43 × 10⁴ watt
B.
4·33 × 10⁴ watt
C.
2·21 × 10⁴ watt
D.
5·65 × 10⁴ watt

Solution:

Total height, h = 6 x 3.5 = 21 m
So total work done, W = mgh = 1000 x 9.8 x 21 = 205800J
Power, P = W/t = 205800 / 6 = 3.43 x 10⁴ watt

QUESTION: 16

The work done by a body is directly proportional to :

A.
Force acting on the body
B.
Displacement produced in the body
C.
Mass of the body
D.
Both (A) and (B)

Solution:

QUESTION: 17

Work done is said to be positive when a force causes displacement:

A.
In its own direction
B.
In the direction opposite to the applied force
C.
In the direction at right angles to the direction of applied force
D.
None of the above

Solution:

QUESTION: 18

The work done on an object does not depends on the

A.
displacement
B.
angle between force and displacement
C.
force applied
D.
initial velocity of the object

Solution:

QUESTION: 19

In which case work is not done:

A.
A girl swimming in a pond
B.
A windmill lifting water from a well
C.
A standing man holding a suit case in his hand
D.
A sail boat moving in the direction of wind

Solution:

QUESTION: 20

In which case work is done:

A.
A green plant carrying out photosynthesis
B.
A porter standing at a place and carry heavy load on his head
C.
Drying of food grains in sun
D.
A trolley rolling down a slope

Solution:

QUESTION: 21

A stone is tied to a string and whirled in a circular path. The work done by the stone is :

A.
negative
B.
zero
C.
positive
D.
none of the above.

Solution:

QUESTION: 22

In order to do work, energy is

A.
transferred or converted
B.
used up
C.
lost
D.
lost or transferred

Solution:

QUESTION: 23

A rocket rises up in the air due to the force generated by the fuel. The work done by the:

A.
fuel is negative work and that of force of gravity is positive work
B.
fuel is positive work and that of force of gravity is negative work
C.
both fuel and force of gravity do positive work
D.
both fuel and force of gravity do negative work.

Solution:

As the rocket moves in the direction of force generated by fuel, therefore it is positive work. As the force of gravity acts in the direction opposite to the displacement. Therefore, it is negative work.

QUESTION: 24

One joule work is said to be done when a force of one newton acts through a distance of: