132) Ultrasonic waves are produced by piezoelectric effect.
133)   Hubble’s law is related with speed of galaxy.
134)    Apparent Weight Of a body falling freely is zero.
135)  In a β-decay the daughter nucleus has one proton more than parent nucleus.
136)   The core of a transformer is laminated so that energy losses due to eddy current can be minimised.
137)    When an external force is applied to a body, the change per unit length along direction of force is called longitudinal strain.
138)     The velocity of sound in any gas depends upon density and elasticity of gas.
139)  The velocity of sound is generally greater in solids than in gases because both density and elasticity of solids are high.
140) The angular momentum of a moving body remains constant if net external torque is not applied.
141)    A circular disc is rotating with angular velocity ‘ω’. If a man standing at edge of disc walks towards its centre, the angular                     velocity of disc will increase
142)  Work done by a simple pendulum in one complete oscillation is zero.143) Surface is both scalar and vector.
143)   Beats are the results of constructive and destructive interference.
144) A sphere is rolled on rough horizontal surface. It gradually slow down and stops. The force of friction tries to decrease linear               velocity.
145) Two glass plates having a little water in between cannot be easily separated because of atmospheric pressure.
146) In a sonometer wire, the produced waves are transverse, stationary and polarized.
147)   A  geo stationary satellite revolve about polar axis.
148) Two waves are said to be coherent, if they have same frequency, phase and amplitude.
149) If the spinning speed of earth is increased, then weight of body at equator decreases.
150)  The MI of rigid body, depends upon distribution of mass from axis of rotation.
151) A person sitting in a open car moving at constant velocity throws a ball vertically up to the air. The balls falls exactly in the hand          which threw it up.
152) A hallow sphere is held suspend. Sand is now poured into it in stages. The centre of gravity of gravity of sphere is first falls and              then rises to original position.
153) Sound is heard with more intensity through CO2 than through air, because of density of CO2  is greater than that of air.The                    velocity of sound in a gas depends on density and elasticity of gas.
154) The dark lines in solar spectrum are due to absorption of certain wavelengths by elements present in outer layer.
155)Temperature of sun can be found out by Stefan-Boltzmann law.
156) A bullet is dropped from same height from where a bullet is fired horizontally. They will hit ground simultaneously.
157)If gymnast sitting on a rotating stool with his arms out stretched suddenly lowers his hands than the angular velocity                               decreases.
158) When an aeroplane moves at a speed higher than velocity of sound in air, a loud bang is heard. This is because it                                    produces a shock wave which is received as a bang.
159) Good absorbers of heat are good emitters.
160) Woollen clothes keep the body warm in winter as air is a bad conductor of heat which is in pores of clothes.
161)The Earth without its atmosphere would be inhospitably cold because all the heat would escape in absence of atmosphere.
162) Scent sprayer is based on Bernoulli’s theorem.
163) The property utilised in manufacture of lead shots is surface tension of liquid lead.
164) It is difficult to move a cycle along the road with its brakes on as sliding friction is greater than rolling friction.