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Q:

A solid ball of metal has a spherical cavity inside it. When the ball is heated the volume of the cavity will

A) increase B) decrease
C) remain unaffected D) have its shape changed
 
Answer & Explanation Answer: A) increase

Explanation:

The metal ball can be considered  to be made up of several layers of thinner ones. On heating each of these layers will increase in radius. As the inner most layer also increases its radius, the volume inside it i.e, the volume of the hollow portion will also increase.

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Q:

In very cold countries alcohol is used as a thermometric liquid because 

A) alcohol is a poor conductor of heat B) alcohol can be coloured for its level to be seen easily
C) its freezing point is very low D) it will not stick to the glass tube
 
Answer & Explanation Answer: C) its freezing point is very low

Explanation:

Alcohol has a freezing point as low as -117oC. So it won't freeze even in very cold countries.

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Q:

A man stands on the pan of a balance holding a fish in his right hand and bucket of water in his left hand. If he transfers the fish into the bucket, the total weight on the pan

A) increases B) decreases
C) remains the same D) first increases and then decreases
 
Answer & Explanation Answer: C) remains the same

Explanation:

Before transferring the fish, the position is the man with the fish and the bucket of water. After transferring the position is : the man without the fish, but the fish inside the water in the bucket. Thus to know whether there is any change in weight, it is enough to consider whether there is any change in weight when the fish in air is transferred into the water. The answer is there is no change as when in water though it loses weight due to upthrust of water on it, the level of water increases and exerts an equal force at the bottom

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Q:

The fact that two large ships travelling on close parallel courses in the same direction tend to move towards each other can be explained by

A) Bernoulli's principle B) Magnetic properties of the ship's material
C) Newton's third law of motion D) Earth's gravitational force
 
Answer & Explanation Answer: A) Bernoulli's principle

Explanation:

The rapid flow of air between the two moving ships causes a reducton of pressure (Bernoulli's principle) , so they (the ships) are drawn closer together

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Q:

A capillary tube is partially dipped vertically in a vessel containing water. Due to capillarity water rises in the tube. The height of water rise in the tube can be increased by 

A) decreasing the radius of the capillary tube B) increasing the radius of the capillary tube
C) increasing the height of water in the vessel D) None of these
 
Answer & Explanation Answer: A) decreasing the radius of the capillary tube

Explanation:

The water rise in a capillary tube dipped in water is such that the weight of water in the tube above the surface of water in the vessel is equal to  the upward force due to surface tension. So it is clear that if the bore to the tube is decreased , the height of the water column in it  must be greater.

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Q:

The inability of a body to change its state of rest or uniform motion along a straight line is called its

A) momentum B) velocity
C) acceleration D) inertia
 
Answer & Explanation Answer: D) inertia

Explanation:

Flows out of Newton's first law of motion.

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Q:

A bucket of water is hung from a spring balance. A piece of iron is suspended in the water without touching the sides or touching the bottom of the bucket. The reading of the spring balance

A) will increase B) will decrease
C) does not change D) varies with the increase of depth of the immersion of the iron piece
 
Answer & Explanation Answer: A) will increase

Explanation:

When the piece of iron is lowered into the water, the water level in the bucket increases. And so the pressure at the bottom of bucket also increases. Thus the total thrust at the botto also increases. Therefore the spring balance reading increases.

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Q:

A piece of ice is floating in water kept in a beaker. When all the ice melts the level of water will

A) first rise and then fall B) fall
C) remain the same D) rise
 
Answer & Explanation Answer: C) remain the same

Explanation:

The submerged portion of the ice on melting shrinks a little in volume. so the level of water goes down a little.But this is just made up by the water added by the melting of upper portion. Addition is equal to the Shrinkage. Hence level is unchanged.

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