2. When is work done by a force zero.
3. (a) Differentiate between upthrust and weight(b)When does an object float or sink.
4. A truck and a car are running with same velocity. Which of the two has less kinetic energy ?
5. A rock that is falling from the top a cliff into the river. The weight of the rock is 750 N. The acceleration of free fall is 10 m/s2. Calculate its kinetic energy just before hitting the water
6. Write any three difference between Transverse and longitudinal Wave?
7. (a) State a condition for an echo to be heard.(b)Bats cannot see then how do they catch their Prey.[1+2]
8.(a) Derive expression of frequency, wavelength and Velocity of wave . (b) A sound wave travels at a speed of 339 m/s ‘ if the wavelength is 1.2 cm, what is the frequency of the wave.
9.A student wishes to work out how much power she uses to lift her body when climbing a flight of stairs. Her body mass is 60 kg and the vertical height of the stairs is 3.0 m. She takes 12 s to walk up the stairs.
(a) Calculate: (i) The work done in raising her body mass as she climbs the stairs,(ii) The output power she develops when raising her body mass.
(b) At the top of the stairs she has gravitational potential energy. Describe the energy transformations taking place as she walks back down the stairs and stops at the bottom.
(c) What is the difference between a gravitational potential energy and kinetic energy?
10. Write the full name of sonar. How will you determine the depth of a sea using echo ranging?
(b) A sonar device on a submarine sends out a signal and receives an echo 5 s later. Calculate
the speed of sound in water if the distance of the object from the submarine is 3625 m.
Or, (a) what is meant by intensity of sound? (b) Mention the conditions for an echo to be heard clearly.
(c) A ball is dropped into a pond from a height of 44.1 m. The splash of sound is heard 3.13 second after the ball is dropped. Determine the velocity of sound in air. 
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