Physics Test 184

Result

Physics Test 184

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Question 1
4 / -1

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

A
23000

B
20000

C
34500

D
23500

Solution
Question 2
4 / -1

The distance covered by a body of mass 5g having linear momentum 0.3kgm∕s in 5s is:

A
0.3m

B
300m

C
30m

D
3m

Solution

P = mv

0.3 = 5/1000 × v ⇒ v = 60m/s

Distance travelled in 5s = 60 × 5

= 300m
Question 3
4 / -1

A particle is released from height S from the surface of the Earth. At a certain height its kinetic energy is three times its potential energy. The height from the surface of earth and the speed of the particle at that instant are respectively

A

B

C

D

Solution
Question 4
4 / -1

Body A of mass 4m moving with speed u collides with another body B of mass 2m, at rest. The collision is head on and elastic in nature. After the collision the fraction of energy lost by the colliding body A is

A
5/9

B
1/9

C
8/9

D
4/9

Solution
Question 5
4 / -1

A mass m is attached to a thin wire and whirled in a vertical circle. The wire is most likely to break when

A
inclined at an angle of 60∘ from vertical

B
the mass is at the highest point

C
the wire is horizontal

D
the mass is at the lowest point

Solution

The tension is maximum at the lowest position of mass, so the chance of breaking is maximum.
Question 6
4 / -1

A moving block having mass m, collides with another stationary block having mass 4m. The lighter block comes to rest after collision. When the initial velocity of the lighter block is v, then the value of coefficient of restitution (e) will be

A
0.5

B
0.25

C
0.8

D
0.4

Solution
Question 7
4 / -1

Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50ms⁻¹. Take 'g' constant with a value 10ms⁻². The work done by the

(i) gravitational force and the

(ii) resistive force of air is

A
(i) 1.25 J - (ii) -8.25 J

B
(i) 100 J - (ii) 8.75 J

C
(i) 10 J - (ii) -8.75 J

D
(i) -10 J - (ii) -8.25 J

Solution

Here

m = 1g = 10⁻³kg,h = 1km = 1000m. v = 50ms⁻¹, g = 10ms⁻²

(i) The work done by the gravitational force

= mgh = 10⁻³ × 10 × 1000 = 10J

(ii) The total work done by gravitational force and the resistive force of air is equal to change in kinetic energy of rain drop
Question 8
4 / -1

Two identical balls A and B having velocities of 0.5ms⁻¹ and 0.3ms⁻¹ respectively collide elastically in one dimension. The velocities of B and A after the collision respectively will be

A
−0.5ms⁻¹ and 0.3ms⁻¹

B
0.5ms⁻¹ and −0.3ms⁻¹

C
−0.3ms⁻¹ and 0.5ms⁻¹

D
0.3ms⁻¹ and 0.5ms⁻¹

Solution

Masses of the balls are same and collision is elastic, so their velocity will be interchanged after collision.

∴ v_a = +u_B = −0.3ms⁻¹ and v_B= v_A = 0.5ms⁻¹
Question 9
4 / -1

A particle of mass 10 g moves along a circle of radius 6.4 cm with a constant tangential acceleration. What is the magnitude of this acceleration if the kinetic energy of the particle becomes equal to 8×10⁻⁴J by the end of the second revolution after the beginning of the motion?

A
0.18m/s²

B
0.2m/s²

C
0.1m/s²

D
0.15m/s²

Solution
Question 10
4 / -1

What is the minimum velocity with which a body of mass m must enter a vertical loop of radius R so that can complete the loop?

A
√3gR

B
√5gR

C
√gR

D
√2gR

Solution

The minimum velocity with which a body of mass m must enter a vertical loop of radius R so that can complete the loop = √5gR