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a) Explain by an examples what is meant by potential energy. Write down the expression for gravitational potential energy of a body of mass m placed at a height h above the surface of the earth. b) What is the difference between potential energy and kinetic energy? c) A ball of mass 0.5 kg slows down from a speed of 5 m/s to that of 3 m/s. Calculate the change in kinetic energy of the ball. State your answer giving proper units. |
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Answer» a) The energy stored in a body due to either its position or change in shape is known as potential energy. Water stored in a reservoir is an example of potential energy. PE = mgh Where, PE is the potential energy m is the mass of the body g is the acceleration due to gravity h is the height above the surface of the earth b) Following are the differences between kinetic energy and potential energy: i) Kinetic energy is defined as the energy in body due to its motion while potential energy is defined as the energy due to its position. ii) Kinetic energy of a body when it is at rest is zero whereas the potential energy of a body when it is at rest is not zero. c) Mass of ball, m = 0.5 kg Speed, v1 = 5 m/s Speed, v2 = 3 m/s KE1 = 1/2 m(v1)2 KE2 = 1/2 m(v2)2 Change in KE = KE1 – KE2 = 4J |
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