Work Energy and Power - Online Test
Q1. work-energy theorem does not give information on
Answer : Option D
Explaination / Solution:
According to work energy theorem :
Net work done on a body equals change in its kinetic energy
So it does not give any information about time dependence.
Q2. Physically, the notion of potential energy is applicable only to
Answer : Option B
Explaination / Solution:
Potential energy is the stored energy of an object. It is the energy by virtue of an object's position relative to other objects. Potential energy is often associated with restoring forces such as a spring or the force of gravity. It is applicable only for conservative forces.
Q3. The work done by a conservative force
Answer : Option A
Explaination / Solution:
A force is said to be conservative if work done by this force is independent of path and is dependent only on end points .
Q4. The total mechanical energy of a system is conserved if the
Answer : Option A
Explaination / Solution:
Mechanical energy is the sum of kinetic and potential energy in an object that is used to do work. In other words, it is energy in an object due to its motion or position, or both. In case of conservative forces total mechanical energy remains conserved because potential energy applicable only for conservative forces.
Q5. For a ball dropped from a tower of height h the total mechanical energy is
Answer : Option C
Explaination / Solution:
mechanical energy = sum of potential and kinetic energies
a falling ball will have both these energies in between topmost and bottomost points of its motion so mechanical energy is the sum of potential and kinetic energies.
Q6. The potential energy of a spring whose spring constant is k and is compressed by x is
Answer : Option B
Explaination / Solution:
If a spring is stretched or compressed by a distance x from its natural length under the action of restoring force then
F = -kx
dU=−F.dx
Q7. mass and energy are equivalent and are related by
Answer : Option A
Explaination / Solution:
Mass–Energy equivalence states that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Einstein's theory of special relativity. It shows that matter (as mass) and energy can be converted into each other according to the famous equation
Q8. Power is defined as
Answer : Option C
Explaination / Solution:
Power is the rate of doing work. It is the amount of energy consumed per unit time. Having no direction, it is a scalar quantity. In the SI system, the unit of power is the joule per second (J/s), known as the watt.
The integral of power over time defines the work performed.
if force is constant
Q9. S.I unit of power is
Answer : Option D
Explaination / Solution:
The SI unit of power, equivalent to one joule per second, corresponding to the rate of consumption of energy (Work done).
Q10. Which of the following laws used to solve problems in collisions?
Answer : Option B
Explaination / Solution:
If external force is absent then linear momentum of system remains conserved. In collision force of impact due to collision is internal and very large.
