Physics Test 156

Result

Physics Test 156

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Question 1
4 / -1

Four similar particles of mass m are orbiting in a circle of radius r is the same direction and same speed because of their mutual gravitational attractive force as shown in the figure. Speed of a particle is given by

A

B

C

D
Zero

Solution
Question 2
4 / -1

A particle moves with a velocity horizontally under the action of constant force The instantaneous power supplied to the particle is :

A
200 W

B
Zero

C
100 W

D
140 W

Solution
Question 3
4 / -1

The potential energy of a long spring when stretched by 2 cm is U. If the spring is stretched by 8 cm, potential energy stored in it will be :

A
4U

B
8U

C
16U

D
2U

Solution
Question 4
4 / -1

A constant torque of 100 N m turns a wheel of moment of inertia 300 kg m² about an axis passing through its centre. Starting from rest, its angular velocity after 3 s is :-

A
1 rad/s

B
5 rad/s

C
10 rad/s

D
15 rad/s

Solution

ω_i = 0

ω_f = ω_i + αt

= 0 + 1/3 x 3

ω_f= 1 rad/sec
Question 5
4 / -1

The ratio of radius of gyration of a solid sphere of mass M and radius R about its own axis to the radius of gyration of the thin hollow sphere of same mass and radius about its axis is :-

A
5 : 3

B
2 : 5

C
√5 : √3

D
√3 : √5

Solution

To solve this problem, we need to find the ratio of the radius of gyration for a solid sphere (K₁) to the radius of gyration for a thin hollow sphere (K₂) of the same mass M and radius R.

The moment of inertia (I) of a solid sphere about its own axis is given by :

The radius of gyration (K) is related to the moment of inertia (I) and mass (M) by the formula :

I = Mk²

So for the solid sphere, we can find K₁ using :

Now, for a thin hollow sphere, the moment of inertia about its axis is given by :
Question 6
4 / -1

An energy of 484 J is spent in increasing the speed of a flywheel from 60 rpm to 360 rpm. The moment of inertia of the flywheel is :

A
0.07 kg-m²

B
0.7 kg-m²

C
3.22 kg-m²

D
30.8 kg-m²

Solution
Question 7
4 / -1

The angular acceleration of a body, moving along the circumference of a circle, is :

A
along the radius towards the centre

B
along the tangent to its position

C
along the axis of rotation

D
along the radius, away from centre

Solution
Question 8
4 / -1

An electric lift with a maximum load of 2000 kg (lift + passengers) is moving up with a constant speed of 1.5 ms⁻¹. The frictional force opposing the motion is 3000 N. The minimum power delivered by the motor to the lift in watts is : (g = 10 ms⁻²)

A
23000

B
20000

C
34500

D
23500

Solution

Fup = 2000 g + 3000

= 23000 N

Minimum power

P_min= Fv = 23000 × 3 / 2

= 34500 W
Question 9
4 / -1

The escape velocity of a body on the earth surface is 11.2 km/s. If the same body is projected upward with velocity 22.4 km/s, the velocity of this body at infinite distance from the centre of the earth will be:

A
11.2√2 km/s

B
Zero

C
11.2 km/s

D
11.2√3 km/s

Solution
Question 10
4 / -1

If R is the radius of the earth and g is the acceleration due to gravity on the earth surface. Then the mean density of the earth will be :

A

B

C

D

Solution