Question

Q] Choose one option for each and explain how it is correct
1) When an object is falling freely then what can you say about its energy?
a) Its kinetic energy is converted into potential energy
b) Its mechanical energy is converted into heat
c) There is no change in its energy
d) Its potential energy is converted into kinetic energy

2) Which of the following statement is correct?
a) Longitudinal waves propagate through solids, liquids and gases
b) Longitudinal waves propagate through solids and liquids
c) Longitudinal or transverse waves don't propagate through gases
d) Longitudinal waves propagate through gases only

3) A piece of ice is floating on the water in a glass completely filled to it brim. What will happen when the ice fully melts?
a) Water will spill out                           b) No change in the water level
c) The level of water will decrease         d) It will depend on the mass of ice

4) If two bodies of different masses have same kinetic energy then which of the following case will be observed?
a) The body of smaller mass will have more momentum
b) The body with greater mass will have more momentum
c) Both the bodies will have same momentum
d) Momentum of both will be zero

5) Earth is revolving around the sun in elliptical orbit. Where its velocity is more?
a) Near the sun                                 b) Away from the sun                
c) Velocity is constant                       d) At extreme of the ellipse

6) At what height will a body of mass 1 kg have potential energy of on joule?
a) 1/980 cm           b) 980 cm           c) 1 meter      d)9.8 meter

7) The periodic time of a sound wave is 1/200 sec. Then what will be its frequency?
a) 100 Hz           b) 200 Hz     c) 20 Hz        d) 340 Hz]

8) What energy is contained in the balloon after air is blown into it and till it bursts?
a) Heat               b) Sound             c) Potential              d) Electrostatic

9) Why salt (sodium chloride) is sprinkled on the ice collected on roads in winter?
a) Coolness of ice is not felt.                  
b) The melting point is lowered.
c) Melting point is raised and ice does not melt.
d) The melting point is lowered and ice melts quickly.

10) When a few drops of spirit (alcohol) are dropped on palm the skin feels cool. Why?
a) Spirit is cool                                        b) Spirit evaporates slowly
c) Heat is absorbed by spirit when it evaporates      d) Spirit evaporates

Answer 1

1) d
2)  a travel thru all

3} b no change in water level

4} KE = 1/2 p² / m    p = momentum = (2 m KE)^1/2    higher mass higher p

5]  the velocity is more when it is nearer to sun than when it is farther away.
     Because earth sweeps the same area in the same time.

6}  potential energy above surface of earth = m g height
           = 1 kg * 9.8 m/s² * height = 1 Joule          height = 1/9.8 m = 1/980 cm

7} Time period T = 1/200 sec. It means that the wave oscillated 1/T times
     in a second. frequency = 200 hertz

8)  potential energy due to volume and Pressure.

9) d.    When the temperature is -10 degrees, ice is solid. We need to wait till
         temp outiside raises to 0 deg. Add salt and then melting point of ice is
         lowered from 0 to -10 deg, and so ice melts at the atmospheric temperature
         of -10 deg.

10)  d  - for evaporation spirit takes heat from palm and so the palm cools