Does oil rise in the wick of the lamp because?
(A) the oil is too light
(B) due to capillary action
(C) due to decrease in surface tension
(D) oil is volatile
The correct answer is Capillary action. The oil in the wick of an oil lamp rises up due to capillary action. This effect is due to surface tension of liquids. The wick here acts as a capillary tube.
The hairs of the shaving brush stick together after coming out of the water, what is the reason for this?
(A) Friction
(B) Surface tension
(C) Elasticity
(D) Viscosity
When the brush is taken out of water, the hairs cling together due to surface tension. This happens because the free surface of water tries to acquire a minimum surface area.
The apparent weight of a person in a lift is less than the actual weight when the lift is moving?
(A) up with acceleration
(B) down at the same speed
(C) up with uniform speed
(D) down with acceleration
An ice cube is floating in a glass of water, when the ice melts, what will be the effect on the water level?
(A) will increase will decrease
(B) first increase then decrease
(C) will remain the same
(D) none of these
When a floating piece of ice melts into water, it contracts by the volume equal to the volume of ice pieces above the water surface while floating on it. Hence, the level of water does not change when ice floating on it melts.
What are the changes in the molecules of an object when it is heated?
(A) the speed will increase
(B) weight will decrease
(C) the load will increase
(D) energy will decrease
When heat is added to a substance, the molecules and atoms vibrate faster. As atoms vibrate faster, the space between atoms increases. The motion and spacing of the particles determines the state of matter of the substance. The end result of increased molecular motion is that the object expands and takes up more space.
In optics, the refractive index of a substance is described by the formula n = c/v, where c is:
(A) the speed of light in medium
(B) the centre of curvature
(C) the radius of the sphere
(D) the speed of light in vacuum
Refractive Index Formulan is the refractive index. c is the velocity of light in a vacuum ( 3 × 108 m/s) v is the velocity of light in a substance.
Who discovered X-rays?
(A) Faraday
(B) Newton
(C) Rutherford
(D) none of these
When a boat enters the sea from a river, then?
(A) rises slightly upwards
(B) sinks slightly
(C) remains unchanged
(D) none of these
The correct answer is It rises a little. A ship rises a little when enters the sea from a river. Because of salinity, seawater has more density than river water. In the sea, the more buoyant force is exerted upon the ship than in the river.
When the speed of a moving object is doubled, then its kinetic energy?
(A) doubles
(B) increases three times
(C) remains the same
(D) quadruples
The change in the kinetic energy of the object as the speed changes is proportional to the square of the factor by which the speed changes. If the speed of the object becomes double, its kinetic energy changes to four times the initial kinetic energy.
If a cyclist goes round a turn, then he
(A) bends outward
(B) bends inwards
(C) leans forward
(D) does not bend at all
A cyclist bends inwards at a turn to balance the centrifugal force with the centripetal force. If the cyclist does not bend on the curve of the road the force will propel him outward of the road and would make him crash.
Get the Examsbook Prep App Today