Worksheet: Work and Energy - Science Class 9

Q.1. Fill in the blank
(i) When a ball is thrown upwards, ________ energy is transformed into ________ energy.
(ii) The sum of the potential and kinetic energies of a body is called ________ energy.
(iii) Work is measured as a product of ________ and _________.
(iv) The electricity meter installed in our home measures electric energy in the units of ______.
(v) The work done on a body moving in a circular path is ___________.

Q.2. How are Joule (J) and ergs (erg) related?
(a) 1J = 10⁷erg
(b) 1erg = 10⁷_J
(c) 1J = 10^-7erg
(d) None

Q.3.  If the force is applied at an angle θ then work done is
(a) W = FS Cos θ  F = Force
(b) W = FS θ S =  Distance
(c) W = FS Sin  θ W = work
(d) None

Q.4. If a body is stored at a height ‘h’ then it will posses:
(a) Kinetic energy
(b) Potential energy
(c) Both
(d) None

Q.5. If the body starts from rest, then change in its kinetic energy is
(a) Positive
(b) Negative
(c) Zero
(d) May be Positive or negative depending upon the mass of the body

Q.6. When do we say that work is done?

Q.7. Define 1 J of work.

Q.8. What is the kinetic energy of an object?

Q.9. What is power?

Q.10. An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?

Q.11. Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

Q.12. Define average power.

Q.13.  In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.

Q.14. Define 1 watt of power.

Q.15. A battery lights a bulb. Describe the energy changes involved in the process.