Physics Test 84

Result

Physics Test 84

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Question 1
4 / -1

A body falling vertically downwards under gravity breaks in two parts of unequal masses. The centre of mass of the two parts taken together shifts horizontally towards :

A
heavier piece

B
lighter piece

C
does not shift horizontally

D
depends on the vertical velocity at the time of breaking

Solution

As horizontal force is zero, centre of mass does not shift horizontally.
Question 2
4 / -1

Which of the following statement is incorrect:

A
Law of conservation of linear momentum is valid in all inertial reference frame

B
Linear momentum is independent of reference frame

C
Total momentum of system is zero in centre of mass frame

D
Kinetic energy depends on frame of reference

Solution

Linear momentum depends on frame of reference as velocity depends on frame of reference.
Question 3
4 / -1

Three thin rods each of length L are arranged in a inverted U, as shown in figure. The two rods on the arms of U each have mass M the third rod has mass 3M. The center of mass of the system from centre of upper rod is:

A
L/3

B
L/2

C
L/5

D
2L/3

Solution
Question 4
4 / -1

A stationary body explodes into four identical fragment such that three of them fly off mutually perpendicular to each other with same kinetic energy E₀. Then total energy of explosion is :

A
4E₀

B
3E₀

C
5E₀

D
6E₀

Solution
Question 5
4 / -1

Two blocks A and B are connected by a massless string as shown. A force of 30N is applied on block B. The distance travelled by centre of mass in 2 second starting from rest is:

A
1m

B
2m

C
3m

D
none of these

Solution
Question 6
4 / -1

A circle of area A lies in the x-y plane in a region, where the magnetic field is given by . Where a, b, c are constant. The magnitude of flux in Wb passing through the circle is:

A
aA Wb

B
(a + b)a Wb

C
bA Wb

D
cA Wb

Solution
Question 7
4 / -1

A square coil of side 25 cm having 1000 turns is rotated with a uniform speed in a magnetic field about an axis perpendicular to direction of field. At an instant t. The emf induced in the coil is e = 200 sin (100πt). The magnetic induction is :

A
0.5 T

B
0.01 T

C
10^–3T

D
0.1 T

Solution
Question 8
4 / -1

An emf induced in a coil, the linked magnetic flux:

A
must decrease

B
must increase

C
must remain constant

D
can be either increased or decreased

Solution
Question 9
4 / -1

In the following figure, the magnet is moved towards the coil with a speed V and induced emf is 'e'. If magnet and coil recede away from one another each moving with speed V, the induced emf in the coil will be :

A
e

B
2e

C
e/2

D
4e

Solution

Apply e ∝ v_rel
Question 10
4 / -1

A square coil ABCD lying in x-y plane with its centre at origin. A long straight wire passing through origin carries a current i = (2t + 2) in negative z-direction. The induced current in the coil is :

A
Clockwise

B
Anticlockwise

C
Alternating

D
Zero

Solution

∵ Plane of coil and magnetic field lines are in same plane.
∴ Flux linked through the coil is zero.