CBSE Class 9 Science – MCQ and Online Tests – Physics – Unit 4 – Work and Energy
Every year CBSE schools conducts Annual Assessment exams for 6,7,8,9,11th standards. These exams are very competitive to all the students. So our website provides online tests for all the 6,7,8,9,11th standard’s subjects. These tests are also very effective and useful for those who preparing for any competitive exams like Olympiad etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.
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CBSE Class 9 Science – MCQ and Online Tests – Physics – Unit 4 – Work and Energy
Question 1.
Two army persons A and B each of weight of 500 N climb up a rope through a height of 10 m. A takes 20 s while B takes 40 s to achieve this task. What is ratio of the powers of person A and B?
(a) 1 : 2
(b) 1 : 4
(c) 2 : 1
(d) 14 : 1
Answer
Answer: (c) 2 : 1
Question 2.
A body is falling from a height h. After it has fallen a height \(\frac{h}{2}\), it will possess
(a) only potential energy
(b) only kinetic energy
(c) half potential and half kinetic energy
(d) more kinetic and less potential energy
Answer
Answer: (c) half potential and half kinetic energy
Question 3.
An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are lo m above the ground, they have the same.
(a) acceleration
(b) momenta
(c) potential energy
(d) kinetic energy
Answer
Answer: (a) acceleration
Question 4.
A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g = 10 ms²)
(a) 6 × 10³ J
(b) 6 J
(c) 0.6 J
(d) zero
Answer
Answer: (d) zero
Question 5.
Which one of the following is not the unit of energy?
(a) joule
(b) newton metre
(c) kilowatt
(d) kilowatt hour
Answer
Answer: (c) kilowatt
Question 6.
Mechanical energy of a body includes
(a) kinetic energy only
(b) potential energy only
(c) kinetic energy and potential energy
(d) none of these
Answer
Answer: (c) kinetic energy and potential energy
Question 7.
The work done on an object does not depend upon the
(a) displacement
(b) force applied
(c) angle between force and displacement
(d) initial velocity of the object
Answer
Answer: (d) initial velocity of the object
Question 8.
Commercial unit of energy is
(a) joule
(b) kWh
(c) watt
(d) newton
Answer
Answer: (b) kWh
Question 9.
Water stored in a dam possesses
(a) no energy
(b) electrical energy
(c) kinetic energy
(d) potential energy
Answer
Answer: (d) potential energy
Question 10.
The number of joules contained in 1 kWh is
(a) 36 × 105 J
(b) 3.6 × 107 J
(c) 36 × 108 J
(d) 3.7 × 107 J
Answer
Answer: (a) 36 × 105 J
Question 11.
Potential energy of a body depends on its
(a) position
(b) configuration
(c) position and configuration
(d) mass and velocity
Answer
Answer: (c) position and configuration
Question 12.
Which of the following graphs best represents graphical relation between momentum P and kinetic energy K for a body in motion?
Answer
Answer: (d)
Question 13.
When a body falls freely towards the earth, then its total energy
(a) increases
(b) decreases
(c) remains constant
(d) first increases and then decreases
Answer
Answer: (c) remains constant
Question 14.
A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car
(a) does not change
(b) becomes twice to that of initial
(c) becomes 4 times that of initial
(d) becomes 16 times that of initial
Answer
Answer: (a) does not change
Question 15.
If speed of a car becomes 2 times, its kinetic energy becomes
(a) 4 times
(b) 8 times
(c) 16 times
(d) 12 times
Answer
Answer: (a) 4 times
Question 16.
Work done by friction
(a) increases kinetic energy of body
(b) decreases kinetic energy of body
(c) increases potential energy of body
(d) decreases potential energy of body.
Answer
Answer: (b) decreases kinetic energy of body
Question 17.
When a coil spring is compressed, the work is done on the spring. The elastic potential energy
(a) increases
(b) decreases
(c) disappears
(d) remains unchanged
Answer
Answer: (a) increases
Question 18.
In case of negative work the angle between the force and displacement is (NCERT Exemplar)
(a) 0°
(b) 45°
(c) 90°
(d) 180°
Answer
Answer: (d) 180°
Question 19.
One joule work is said to be done when
(a) a force of 1 N displaces a body by 1 cm
(b) a force of 1 N displaces a body by 1 m
(c) a force of 1 dyne displaces a body by 1 m
(d) a force of 1 dyne displaces a body by 1 cm.
Answer
Answer: (b) a force of 1 N displaces a body by 1 m
Question 20.
SI unit of power is
(a) watt
(b) joule
(c) newton
(d) metre
Answer
Answer: (a) watt
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