401. Which physical quantity is represented by the ratio of momentum and velocity of the body?
1. Velocity
2. Acceleration
3. Mass
4. Force
Option “3” is correct. Momentum is a vector quantity that is the product of Mass and the Velocity of an object or particle. Momentum = Mass × Velocity So, Mass = (Momentum )/Velocity
402. The energy of wind is-
1. Only potential
2. Only kinetic
3. Electrical
4. Potential and kinetic both
Option “2” is correct. The kinetic energy is the energy in moving objects or mass. The kinetic energy of the wind (wind energy) can be converted into electrical or mechanical energy.
Option “1” is correct. The conversion of light energy into electrical energy is based on the phenomenon called photovoltaic effect. Silicon is most widely used semiconductor material for construction photovoltaic cell.
404. What is the correct equation for finding the acceleration?
1. a = (v-u)/t
2. a = u + vt
3. a = (v+u)/t
4. a=(v+u)/2
Option “1” is correct. As we know v = u + at or at = v – u ∴a=(v-u)/t Where, v = ultimate velocity of the particle u = initial velocity of the particle a = Acceleration, t = time
405. A drop of water is spherical in shape. This is due to:
1. Surface tension
2. Low temperature
3. Air resistance
4. Viscosity of water
Option “1” is correct. The shape of a drop of rain is constrained by the surface tension, which tries to give it the shape for which the surface area is minimum for the given volume. The spherical shape has the minimum surface area. That’s why rain drops acquire spherical shape.
406. Velocity of light is maximum in-
1. Diamond
2. Water
3. Vacuum
4. Hydrogen
Option “3” is correct. The speed of light in vacuum is maximum (c = 3 × 108 ms–1). The speed of light decreases gradually in optically denser mediums like water or glass. It is least in diamond.
407. The name of the equipment used for measuring blood pressure is:
Option “2” is correct. Sphygmomanometer is used to measure blood pressure.
408. The force of friction between two surfaces will increase if:
1. A layer of lubricant is kept between the two surfaces
2. The two surfaces are pressed harder
3. Air gap is created between the two surfaces
4. Irregularities on both the surfaces are removed
Option “2” is correct. The force of friction between two surfaces will increase if the two surfaces are pressed harder.
409. An image formed by a plane mirror, that cannot be obtained on a screen is called _______.
French 
English