Physics Test 203

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Physics Test 203

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Weekly Quiz Competition

Question 1
4 / -1

The self inductance of an electric fan motor is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of

A
1 μF

B
2 μF

C
4 μF

D
8 μF

Solution
Question 2
4 / -1

A car of mass 800 kg moves on a circular track of radius 40 m. If the coefficient of friction is 0.5, then the maximum velocity with which the car can move is

A
7 m/s

B
14 m/s

C
8 m/s

D
12 m/s

Solution

When a car goes round a curved road, it requires some centripetal force. While rounding the curve, the wheels of the car have a tendency to leave the curved path and regain the straight line path. Force of friction between the wheels and the road opposes this tendency of the wheels. This force (of friction) therefore acts, towards the centre of the circular track and provides the necessary centripetal force.
Question 3
4 / -1

Directions: This question has two statements, Statement 1 and Statement 2. Of the four choices given after the statements, choose the one that best describes the two statements.

Statement 1: Davisson-Germer experiment proved the wave nature of electrons.

Statement 2: If electrons have wave nature, then they can interfere and show diffraction.

A
Both statements are true. Statement 2 is the correct explanation for Statement 1.

B
Both statements are true. Statement 2 is not the correct explanation of Statement 1.

C
Statement 1 is true, but Statement 2 is false.

D
Statement 1 is false, but Statement 2 is true.

Solution

Davisson-Germer experiment showed that electron beams can undergo diffraction, when passed through atomic crystals. This shows the wave nature of electrons as waves can exhibit interference and diffraction.
Question 4
4 / -1

A semi circular wire of radius 'r' is charged uniformly with a charge 'Q' as shown in the figure. Then, the force experienced by a charge 'q' kept at its centre is

A

B

C

D

Solution

Consider a small charge element dQ at an angle θ subtending a small angle element dθ with centre.

Force between the charges q and dQ is

Resolving the components of the force dF cosθ along x-axis and dF sinθ along y-axis, the components dF sinθ will cancel each other, dF cosθ will add up.

Therefore, resultant force on the charge q,
Question 5
4 / -1

A shell is fired from a cannon with a speed of 100 ms^-1 at an angle 30° with the vertical (y-direction). At the highest point of its trajectory, the shell explodes into two fragments of masses in the ratio 1 : 2. The lighter fragment moves vertically upwards with an initial speed of 200 ms-1. What is the speed of the heavier fragment at the time of explosion?

A
125 ms^-1

B
150 ms^-1

C
175 ms^-1

D
200 ms^-1

Solution
Question 6
4 / -1

Consider a solid sphere of mass M and radius R. The energy released in forming this solid sphere is

A

B

C

D

Solution
Question 7
4 / -1

A block of mass m is placed on a surface with a vertical cross-section given by y = x³/6. If the coefficient of friction is 0.5, then the maximum height above the ground at which the block can be placed without slipping is

A
1/2 m

B
1/6 m

C
2/3 m

D
1/3 m

Solution
Question 8
4 / -1

The logic gate circuit shown in the figure realises which of the following functions?

A
XOR

B
XNOR

C
Half adder

D
Full adder

Solution
Question 9
4 / -1

A horizontal force of 10 N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is 0.2. The weight of the block is-

A
20 N

B
50 N

C
100 N

D
2 N

Solution

Frictional force balances the weight of the body

Frictional force f = μN = mg

f= 0.2 X 10 = 2N

Therefore, the weight of the block mg= 2N
Question 10
4 / -1

The magnetism of a magnet is due to which of the following?

A
Earth

B
Cosmic rays

C
Spin motion of electrons

D
Pressure of a big magnet inside the Earth

Solution