Assertion (A) : The weight of human being on the moon is 1/6 in comparison to earth.
Reason (R) : The moon does not have gravity like earth.
Select the correct answer from following codes –
(A) and (R) are true, and (R) is the correct explanation of
(A).
Correct Answer:
(C) is true, but (R) is false.
The Moon is the Earth's only natural satellite. The surface gravity of the moon is only 1/6 that of the Earth. So, the weight of human being on the moon will be 1/6 of that on the earth. Hence, assertion is true, but reason is false.
Ques: 2
If the gravitational force of the earth suddenly disappears, which of the following will be the correct consequence?
Correct Answer:
(A) The weight of an object will become zero but the mass will remain the same.
If the gravitational force of the earth suddenly disappears, then the weight of an object will become zero but the mass will remain the same.
Ques: 3
Satellite is kept moving in its orbit around the Earth; it is due to –
Correct Answer:
(B) Centripetal force
Centripetal force is a real force that counteracts the centrifugal force and prevents the object from 'flying out,' keeping it moving instead with a uniform speed along a circular or elliptical path. Gravity is the centripetal force that keeps planets moving around the sun and satellites moving around planets.
Ques: 4
The known forces of nature can be divided into four classes, viz, gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them which one of the following statements is not correct?
Correct Answer:
(A) Gravity is the strongest of the four
Gravitational force is the weakest force among the four fundamental forces while strong nuclear force holds the position of strongest force among them.
Ques: 5
A man is standing on a sensitive balance. If he inhales deeply, the reading of the balance –
Correct Answer:
(A) Increases
The reading of the balance increases if the person inhales deeply. One liter of air weighs about 1.225 g. A maximal 4.8 liters breath (average vital capacity for males) weighs approximately 5.88g. Inhaled air will add to the mass of the man and thus his weight goes up slightly.
Ques: 6
As the train starts moving, the head of the passenger sitting inside leans backward because of –
Correct Answer:
(A) Inertia of Rest
According to the Newton's first law of motion sometimes referred to as the law of inertia which states that an object at rest stays at rest and in motion remain in motion with same speed and in the same direction unless acted upon by an external force. When a train suddenly starts, the passenger tends to fall backward. This is because the lower part of the body which is in contact with the train begins to move while the upper part of the body tends to maintain its position due to inertia of rest. As a result, the upper part tends to fall backward.
Ques: 7
Consider the following statements.
Assertion (A): A man standing on a completely frictionless surface can propel himself by whistling.
Reason (R): If no external force acts on a system, its momentum cannot change.
Choose the correct option among the following:
Correct Answer:
(B) Both A and R are true but R is not a correct explanation of A
First statement can be explained on the basis of Newton's third law of motion, "For every action, there is equal and opposite reaction." While whistling, a man uses his breath as a propellant to propel himself. Momentum is the property that a moving object has due to its mass and motion. Hence, when there is no external force applied on any moving object, its momentum cannot change. Hence, statement A and R both are correct but R is not a correct explanation of A.