Physics Test-29

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Physics Test-29

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Question 1
4 / -1

The distance-time graph for a body moving at uniform speed is:

A
A hyperbola

B
A straight line

C
An ellipse

D
A parabola

Solution

The distance-time graph for a body moving with uniform speed is a straight line.
Uniform motion is defined as the speed where the speed does not change with time, only distance and time change.

We know that,
Speed \(={\frac{Distance}{Time}}\)
Since speed remains constant, we can conclude that distance and time are directly proportional to each other.
Therefore, the graph between distance and time is a straight line.
Question 2
4 / -1

The phenomenon by which stars recedes from each other is explained by:

A
black hole theory

B
neutron star theory

C
white dwarf

D
red shift

Solution

The phenomenon by which stars recedes from each other is explained by red shift.
Question 3
4 / -1

A nucleus at rest splits into two nuclear parts having radii in the ratio 1 : 2 Their velocities are in the ratio:

A
8 : 1

B
6 : 1

C
4 : 1

D
2 : 1

Solution

According to the law of conservation of momentum, if no external force acts on it in a system or body then total momentum is conserved. The linear momentum of a body is given by,
Momentum \(=\) mass \(\times\) velocity
In the nucleus, neutrons are closely packed in a small radius. The cube of the radius (r) of the nucleus is proportional to the mass number (m).
\(r ^{3} \propto m\)
or \(\left(\frac{r_{1}}{r _{2}}\right)^{3}= \frac{m _{1}}{m _{2}}\)
Given,
\(\frac{r _{1} }{r _{2}}=\frac{1 }{ 2}\)
Momentum \(= mv\)
By conservation of momentum,
\(m _{1} v _{1}= m _{2} v _{2}\)
\(\frac{v _{1} }{ v _{2}}=\frac{ m _{2} }{ m _{1}}\)
Also from, \(\left(\frac{r_{1} }{r_{2}}\right)^{3}=\frac{m_{1} }{m_{2}}\)
\(\therefore \frac{ v _{1} }{ v _{2}}=\frac{ m _{2} }{ m _{1}}=\left( \frac{r _{2} }{r _{1}}\right)^{3} \)
\(\Rightarrow \frac{ v _{1} }{ v _{2}}=\left(\frac{2 }{ 1}\right)^{3}\)
\(\Rightarrow \frac{ v _{1} }{ v _{2}}=\frac{8 }{ 1}\)
\(\therefore v _{1} :v _{2}=8:1\)
Question 4
4 / -1

The coolant in a chemical or a nuclear plant (i.e., the liquid used to prevent the different parts of a plant from getting too hot) should have:

A
Low specific heat

B
High specific heat

C
High Latent heat

D
None of the above

Solution

The coolant in a chemical or nuclear plant must have a high specific heat as it is known that higher the specific heat of the coolant, higher is its heat-absorbing capacity and vice-versa.
Thus, a liquid which has a high specific heat is the best coolant to be utilized in a nuclear or chemical plant. This prevents different parts of the plant from becoming too hot.
Question 5
4 / -1

A horse is running on a playground and comes to a skidding stop. The force applied on the horse due to the playground is \(500N\). Which is directly opposed to the motion of the horse. How much work does the horse do on the playground?

A
\(500J\)

B
Zero

C
\(100J\)

D
In sufficient data

Solution

The stopping force and the displacement make an angle of \(180^{\circ}(\pi\) rad \()\) with each other.
Thus, work done by the road,
\(\mathrm{W}_{\mathrm{r}}=\mathrm{Fd} \cos \theta=500 \times 0 \times \cos \pi=0\)
Question 6
4 / -1

Which of the following properties shows that light is a transverse wave?

A
Reflection

B
Interference

C
Diffraction

D
Polarization

Solution

Polarizationshows that light is a transverse wave.
The polarization phenomenon, verifies the transverse nature of light. Since sound has longitudinal nature, so it does not show polarization effect.
Question 7
4 / -1

A moving coil galvanometer can be converted into a ammeter by connecting ___________ to the moving coil galvanometer.

A
A low resistance in series

B
A low resistance in parallel

C
A high resistance in parallel

D
A high resistance in series

Solution

A galvanometer can be converted into an ammeter by connecting a shunt resistance in parallel to it.

The shunt resistance should have very low resistance. So, the ammeter (the parallel combination of galvanometer and shunt resistance) will have low resistance.

To convert a galvanometer into an ammeter of current rating \(‘I’\), a small resistance \(‘S’\) (shunt resistance) is connected in parallel across the galvanometer.

\(V_g=\left(I-I_g\right) S=I_g R_g\)

Where \(V_g\) is the voltage across the galvanometer, I is current in the circuit, \(I_g\) is the current is galvanometer, \(R _{ g }\) is the resistance of galvanometer and \(S\) is the resistance of the shunt.

A moving coil galvanometer can be converted into a ammeter by connecting a low resistance in in parallel to the moving coil galvanometer.
Question 8
4 / -1

The minimum external force needed to move a block kept on a rough surface is 250 N. Find the coefficient of friction between the surface and the block if the mass of the block is 40 kg. (g = 10 m/s²)

A
0.3

B
0.45

C
0.625

D
0.825

Solution

Given,
Applied force (F) = 250 N
Mass (m) = 40 kg
Normal (N) = mg = 40× 10 = 400 N
Friction force (f) = μ N = 400μ
For moving the block, Applied (F) ≥ Friction force
250≥ 400μ
As the givenforce is minimum force, so
400μ = 250
∴ Coefficient of friction (μ) = \(\frac{250}{400}\) = 0.625
Question 9
4 / -1

When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by __________.

A
Conduction

B
Convection

C
Radiation

D
Conduction and convection

Solution

Thermal radiation generates from the emission of electromagnetic waves. These waves carry the energy away from the emitting object. Radiation occurs through a vacuum or any transparent medium (either solid or fluid). Thermal radiation is the direct result of random movements of atoms and molecules in matter.
Question 10
4 / -1

A piece of wood has dimensions \(a, b\) \(c\) Its relative density is \(d\). It is floating in water such that the side \(c\) is vertical. It is now pushed down gently and released. The time period is:

A
\(T=2 \pi \sqrt{\left(\frac{a b c}{g}\right)}\)

B
\(T=2 \pi \sqrt{\left(\frac{b a}{d g}\right)}\)

C
\(T=2 \pi \sqrt{\left(\frac{g}{d c}\right)}\)

D
\(2 \pi \sqrt{\frac{\mathrm{da}}{\mathrm{g}}}\)

Solution

We know that:
Time period of SHM of small vertical oscillations in a liquid is given by:
\(T=2 \pi \sqrt{\frac{l}{g}}\), where \(l\) is the length of cube/cylinder dipped in the water.
So according to law of floatation,
weight of the cube \(=\) weight of the water displaced
\(a b c \times d \times g=b c l \times l \times g\)
\(\Rightarrow l=d a\)
\(\Rightarrow T=2 \pi \sqrt{\frac{d a}{g}}\)

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Physics Test-29

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Physics Test-29

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SHARING IS CARING

Question 1

A hyperbola

A straight line

An ellipse

A parabola

Solution

Question 2

black hole theory

neutron star theory

white dwarf

red shift

Solution

Question 3

8 : 1

6 : 1

4 : 1

2 : 1

Solution

Question 4

Low specific heat

High specific heat

High Latent heat

None of the above

Solution

Question 5

\(500J\)

Zero

\(100J\)

In sufficient data

Solution

Question 6

Reflection

Interference

Diffraction

Polarization

Solution

Question 7

A low resistance in series

A low resistance in parallel

A high resistance in parallel

A high resistance in series

Solution

Question 8

0.3

0.45

0.625

0.825

Solution

Question 9

Conduction

Convection

Radiation

Conduction and convection

Solution

Question 10

\(T=2 \pi \sqrt{\left(\frac{a b c}{g}\right)}\)

\(T=2 \pi \sqrt{\left(\frac{b a}{d g}\right)}\)

\(T=2 \pi \sqrt{\left(\frac{g}{d c}\right)}\)

\(2 \pi \sqrt{\frac{\mathrm{da}}{\mathrm{g}}}\)

Solution

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