Topic: UNIT IV: Work, Energy and Power



Topic: UNIT IV: Work, Energy and Power
Q.1
A uniform force of (2iˆ+ ˆj) N acts on a particle of mass 1 kg. The particle displaces from position (3 ˆj + ˆk ) m to (5iˆ+ 3ˆj) m. The work done by the force on the particle is
A. 9 J
B. 6 J
C. 10 J
D. 12 J
Answer : Option C
Explaination / Solution:
No Explaination.


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Q.2
A ball of mass 1 kg and another of mass 2 kg are dropped from a tall building whose height is 80 m. After, a fall of 40 m each towards Earth, their respective kinetic energies will be in the ratio of
A. √2 : 1
B. 1 : √2
C. 2 : 1
D. 1 : 2
Answer : Option D
Explaination / Solution:
No Explaination.


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Q.3
A body of mass 1 kg is thrown upwards with a velocity 20 m s−1. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction?. (Take g= 10ms-2
A. 20 J
B. 30 J
C. 40 J
D. 10 J
Answer : Option A
Explaination / Solution:
No Explaination.


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Q.4
An engine pumps water continuously through a hose. Water leaves the hose with a velocity v and m is the mass per unit length of the water of the jet. What is the rate at which kinetic energy is imparted to water ?.
A. ½ mv2 
B. mv2 
C. ½ mu2 
D. mu2 
Answer : Option A
Explaination / Solution:
No Explaination.


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Q.5
A body of mass 4 m is lying in xy-plane at rest. It suddenly explodes into three pieces. Two pieces each of mass m move perpendicular to each other with equal speed v. The total kinetic energy generated due to explosion is
A. mv2 
B. 3/2 mv2
C. 2mv2 
D. 4mv2
Answer : Option B
Explaination / Solution:
No Explaination.


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Q.6
The potential energy of a system increases, if work is done
A. by the system against a conservative force
B. by the system against a non-conservative force
C. upon the system by a conservative force
D. upon the system by a non-conservative force
Answer : Option A
Explaination / Solution:
No Explaination.


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Q.7
What is the minimum velocity with which a body of mass m must enter a vertical loop of radius R so that it can complete the loop?
A. √(2gR)
B. √(3gR)
C. √(5gR)
D. √(gR)
Answer : Option C
Explaination / Solution:
No Explaination.


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Q.8
The work done by the conservative force for a closed path is
A. always negative
B. zero
C. always positive
D. not defined
Answer : Option B
Explaination / Solution:
No Explaination.


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Q.9
If the linear momentum of the object is increased by 0.1%, then the kinetic energy is increased by
A. 0.1 %
B. 0.2%
C. 0.4%
D. 0.01%
Answer : Option B
Explaination / Solution:
No Explaination.


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Q.10
If the potential energy of the particle is ­α - β/2 x2, then force experienced by the particle is
A. F=β/2 x2 
B. F=βx
C. F=-βx
D. F=-β/2 x2
Answer : Option C
Explaination / Solution:
No Explaination.


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