Physics Test 55

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Physics Test 55

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Question 1
4 / -1

The ratio of radii of the earth to another planet is 2/3 and the ratio of their mean densities is 4/5. If an astronaut can jump to a maximum height of 1.5 m on the earth, with the same effort, the maximum height he can jump on the planet is

A
1 m

B
.8 m

C
. 55m

D
2 m

Solution
Question 2
4 / -1

At what absolute temperature T is the root mean square speed of a hydrogen molecule equal to its escape velocity from the surface of the moon? The radius of the moon is R,g is the acceleration due to gravity on the moon's surface, m is the mass of a hydrogen molecule and k is the Boltzmann constant.

A
mgR / 2K

B
2mgR / K

C
3mgR / 2K

D
2mgR / 3k

Solution
Question 3
4 / -1

The graph shows the dependence of velocity on time for a body that is restricted to move in one dimension, along the x-axis. At t = 0, the body is at rest at x = 0.

At t = 60 sec, the body is located at

A
x = 0 m

B
x = 40 m

C
x = 6 m

D
x = -60 m

Solution

From the graph, as it seems the body at t = 60 sec, the body is located at x = 0 m. The body first constantly increases its velocity and then decreases it.

Therefore, clearly, the answer will be 0.

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

A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distances of 2 m and 3 m, respectively, from the source. The ratio of intensities of the waves at P and Q is

A
9 : 4

B
2 : 3

C
3 : 2

D
4 : 9

Solution
Question 5
4 / -1

A truck and car are moving on a plane road with the same kinetic Energy. They are brought to rest by the application of brakes which provide equal retarding forces. Which one of the following statements is true?

A
Distance traveled by truck is shorter than a car before coming to rest

B
Distance traveled by car is shorter than truck before coming to rest

C
Distance traveled depends on the individual velocity of both the vehicles

D
Both will travel same distance before coming to rest

Solution

By the work-energy theorem, we know

KE_f- KE_i=Work done

So in this case, Initial K.E.=retarding force k×distance traveled

Since kinetic energy is the same and retarding force is the equal distance traveled will be the same.

Hence, the correct option is (D).
Question 6
4 / -1

Two particles execute SHM of the same amplitude and frequency along the same straight line. If they pass each other when going in opposite directions, each time their displacement being half their amplitude, the phase difference between them is

A
π / 2

B
π / 6

C
2π / 3

D
2π / 7

Solution
Question 7
4 / -1

Two rods having thermal conductivity in the ratio of 5: 3 and having an equal length and equal cross-section are joined face to face. If the temperature of free-end of the first rod is 100^∘C and the free end of the second rod is 20^∘C, then calculate the temperature of junction:

A
50^∘C

B
70^∘C

C
85^∘C

D
100^∘C

Solution
Question 8
4 / -1

In an ammeter 10% of the main current is passing through the Galvanometer. If the resistance of the Galvanometer is G, then the shunt resistance, in ohms, is

A
9G

B
G/9

C
90G

D
G/90

Solution
Question 9
4 / -1

What is the effect on the interference fringes in Young's double slit experiment if the width of the source slit is increased?

A
The fringe width increases.

B
The fringe width decreases.

C
The fringes become more distinct.

D
The fringes become less distinct.

Solution

When the widths of the two slits are increased, the fringes become brighter. However, the width of each slit should be considerably smaller than the separation between the slits. When the slits become so wide that this condition is not satisfied, the interference pattern disappears i.e., The fringes become less distinct.

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

The total energy of the electron in the first excited state of hydrogen is −3.4eV. What is the kinetic energy of the electron in this state?

A
+1.7 eV

B
+3.4 eV

C
+6.8 eV

D
+13.4 eV

Solution