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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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Q:

The force that keeps a body in a circular motion called 

A) the centripetal force B) the centrifugual force
C) the frictional force D) all the above
 
Answer & Explanation Answer: A) the centripetal force

Explanation:

without this centripetal force, circular motion is not possible. It acts radially towards the centre and if this force is removed there will be no circular motion but the revolving body will fly off at a tangent.

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Q:

A boy is swinging a ball attached to a string in a horizotal circle. If the string snaps 

A) the ball will travel towards the center of the circle and fall down B) it will continue to travel along a tangent to the circle at the point the ball was at the time of snapping and finally fall down
C) it will fall down at the same place where the string breaks D) None of these
 
Answer & Explanation Answer: B) it will continue to travel along a tangent to the circle at the point the ball was at the time of snapping and finally fall down

Explanation:

The centripetal force having been removed the body cannot  execute the curved path

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Q:

What is the minimum velocity required for a rocket to overcome earth's gravity and travel into space?

A) 18 km/sec B) 11.2 km/sec
C) 21 km/sec D) 35 km/sec
 
Answer & Explanation Answer: B) 11.2 km/sec

Explanation:

This 11.2 km/s is also known as the escape velocity. It works out to roughly 25000miles per hour 

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