Correct Answer:
(B)
Pressure
Force, velocity and acceleration are the examples of vector quantity while pressure is a scalar quantity. Pressure is defined as the force per unit area. It is the force acting in all direction on an area while force is a pull or push in a specific direction.
Ques:
12
Cycle and cars used ball bearing, because-
Correct Answer:
(C)
The effective area of contact between the wheel and axle is reduced.
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. Due to ball bearing, the effective area of contact between the wheel and axle is reduced and hence, the frictional force also reduced.
Ques:
13
The working principle of a washing machine is:
Correct Answer:
(A)
Centrifugation
The working principle of a washing machine is based on centrifugation. Centrifugation is a technique which involves the application of centrifugal force to separate particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed.
Ques:
14
Consider the following statements: A Simple Pendulum is set into oscillation. Then:
The acceleration is zero when the bob passes through the mean position.
In each cycle the bob attains a given velocity twice.
Both acceleration and velocity of the bob are zero when it reaches its extreme position during the oscillation.
The amplitude of oscillation of the simple pendulum decreases with time.
Which of these statements are correct?
Correct Answer:
(C)
1, 2 and 4
When an object, which is in simple periodic motion passes through its mean position then,
No force acts on it.
Its acceleration becomes zero.
Maximum velocity.
Maximum kinetic energy.
Potential energy is zero.
Ques:
15
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:
16
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:
17
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:
18
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:
19
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:
20
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.