Physics Test 52

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Physics Test 52

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Question 1
4 / -1

A gas expands adiabatically at constant pressure, such that its temperature is T ∝ 1/√V. The value of C_P/C_V of the gas is

A
1.3

B
1.5

C
1.67

D
2

Solution

Key Idea Sudden expansion is an adiabatic operation. Adiabatic relation between p and V is pV^γ=k,a constant.

A change in pressure and volume of a gas in which temperature also changes is called an adiabatic change. In such a change, no heat is allowed to enter into or escape from the gas (ie, there is no exchange of heat between the gas and its surroundings). For adiabatic expansion, we have the formula
Question 2
4 / -1

A particle of charge q moves with a velocity The magnitude of the force experienced by the particle is

A
Zero

B
qa (b + c)

C

D
None of these

Solution
Question 3
4 / -1

When a body moves in a circular path, no work is done by the force since

A
Force and displacement are perpendicular to each other

B
The force is always away from the centre

C
There is no displacement

D
There is no net force

Solution

The work done by a force in moving a body is

where is the displacement vector.

In a circular path, the force is centripetal, thus always acting towards the center along the radial direction.

However, the displacement is always along the tangent to the circle at the instantaneous position of the object.

Hence, the correct option is (A).
Question 4
4 / -1

A cricket bat is cut at the location of its center of mass as shown. Then,

A
The bottom piece will have a greater mass

B
The two pieces will have same mass

C
The handle piece will have a greater mass

D
The mass of the handle piece will be double the mass of the bottom piece

Solution

As there is more material near the bottom end of the bat, the centre of mass of the bat is nearer the bottom end of the bat. The bat will balance horizontally on a knife-edge placed at the centre of mass. Centre of the mass is the point about which the rigid body can be balanced. The centre of mass of the handle piece and the bottom piece are at distances d₁and d₂ respectively from the centre of mass of the entire bat.

For the rotational equilibrium, we have M₁d₁ = M₂d₂ where M1 and M₂are the masses of the handle piece and the bottom piece respectively. The distance d₁ is greater than d₂ since the handle piece has thinner regions compared to the bottom piece.

Therefore, M₂> M₁

Hence, the correct option is (A).
Question 5
4 / -1

The resistance of a wire at room temperature 30^∘C is found to be 10Ω. Now, to increase the resistance by 10% the temperature of the wire must be [The temperature coefficient of resistance of the material of wire is 0.002^∘C].

A
36^∘C

B
83^∘C

C
63^∘C

D
33^∘C

Solution
Question 6
4 / -1

If the pitch of the sound from a source appears to drop by 10% to a moving person, then what is the velocity of motion? (Velocity of sound =330 m/s)

A
33 m/s

B
40 m/s

C
53 m/s

D
62 m/s

Solution

Since, the pitch of the sound appears to decrease, so the person is moving away from the observer.

Hence, the correct option is (A).
Question 7
4 / -1

A man pushes against a wall, but fails to move it. He did

A
negative work

B
positive work, but not maximum work

C
maximum positive work

D
no work at all

Solution

The expression for the work done is as follows:

W= Fs

Here, F is the applied force and s is the displacement.

The work is to be done when the applied force on the object displaces it to some distance.

The work done is negative when the body displaces in an opposite direction to the applied force.

The work done is positive when the body displaces in the same direction as the applied force.

In the given problem, a man pushes a wall and fails to displace it. He does not do any work as the wall is not displaced in this case.

Therefore, the work done in this case is zero.

Hence, the correct option is (D).
Question 8
4 / -1

The inductance of a coil is L=10H and resistance R=5Ω. If the applied voltage of the battery is 10 V and it switches off in 1 millisecond. Find induced electromotive force of inductor?

A
2 × 10⁴ V

B
1.2 × 10⁴ V

C
2 × 10^-4 V

D
None of the above

Solution
Question 9
4 / -1

A man travels 1 mile due east, then 5 miles due south, then 2 miles due east and finally 9 miles due north. His displacement is

A
3 miles

B
5 miles

C
4 miles

D
Between 5 and 9 miles

Solution

Consider the initial position is at the origin, and North is +Y axis, South being negative Y axis, East is positive X-axis and west is the negative X-axis.

Then starting from origin,

After 1 miles due east, his coordinates are (1,0)

After 5 miles due south, his coordinates become (1,−5)

After 2 miles due east, his coordinates are ( 1+2,−5) i.e (3,−5)

After 9 miles due north , his coordinates are (3,−5+9) i.e (3,4)

Hence, distance from the initial position is

Hence, the correct option is (B).
Question 10
4 / -1

A vehicle of mass m is moving on a rough horizontal road with momentum P. If the coefficient of friction between the tyres and the road be μ, then the stopping distance is

A
P / 2μmg

B
P² / 2μmg

C
P / 2μm²g

D
P² / 2μm²g

Solution