Physics Test 111

Result

Physics Test 111

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Question 1
4 / -1

The Dimension of σb⁴ (σ = Stefan's constant and b = Wein's Constant) are :

A
[ML⁴T^-3]

B
[M⁰L⁰T⁰]

C
[ML^-2T]

D
[ML⁶T^-3]

Solution

Surface tension = Force/Length = newton/metre.
Question 2
4 / -1

An athlete completes one round of a circular track of radius R in 40 seconds. The displacement at the end of 2 minutes 20 seconds is

A
0

B
2R

C
2πR

D
πR

Solution

2 min 20 second = 140 second.

he completed one round in 40 second.

in 140 second, he will cover = 140/40=3.5 round.

after 3.5 round, he would be on the opposite side of the starting point.

So the displacement will be the diameter or 2R.
Question 3
4 / -1

A body slides down a smooth curved track which is one quadrant of a circle having radius 10 m. The speed of the body at the bottom of the track is:

A

B
10 m/s

C
2 m/s

D
None of these

Solution
Question 4
4 / -1

A particle of mass m is driven by a machine that delivers a constant power k watts. If the particle starts from rest the force on the particle at time t is

A

B

C

D

Solution

Constant power acting on the particle of mass m is k watt.
Question 5
4 / -1

An engine pumps up 100 kg of water through a height of 10m in 5 sec then if the efficiency of the engine os 60% then calculate the power of the engine where g = 10m/s

A
33 kW

B
3.3 kW

C
0.33 kW

D
0.033 kW

Solution

Output power = mgh/t

= 100 kg × 10 m/s² × 10 m / 5 s

= 2 × 10³ Watt

= 2 kW

Effeciency = [(Output power) / (Input power)] × 100

60 = [2 kW / (Input power)] × 100

Input power = 3.33 kW

Power of engine is 3.33 kW
Question 6
4 / -1

A block of mass 4 kg is placed on a rough horizontal plane. A time dependent force F = k t acts on the block, where k = 2 N/s² Force of friction between block and the plane at t = 2 sec (given coefficient of friction is 0.3)

A
4N

B
8N

C
12N

D
zero

Solution

Normal Force, N = mg = 40N

Maximum Frictional Force, fmax=μN=0.2×40 = 8N

As at time t=2s,

F=kt=2×2=4N, which is less than the maximum frictional force which can be applied. So the block wont move and the friction force will be equal to the force applied which is 4N. (i.e f=4N)
Question 7
4 / -1

A particle collides with another particle such that the second particle starts moving and the first particle stops just after the collision. Then which of the following conditions must always be valid? (m/M = ratio of masses)

A
m/M < 1

B
m/M = 1

C
e = 1

D
e < 1

Solution

It m = m and mu, + mu₂ + o = mv

mu₂ = m (v - u₁)

m/m = v - u₁/u₂ ≤ 1
Question 8
4 / -1

A sphere has a perfectly elastic oblique collision with another identical sphere, which is initially at rest. The angle between their direction after the collision is

A
0°

B
60°

C
90°

D
120°

Solution
Question 9
4 / -1

Two bodies having masses in the ratio of 3 : 1 possess the same kinetic energy. The ratio of their linear momentum is

A
1 : 4

B
2 : 1

C
1 : 3

D
√3 : 1

Solution

P = √2 mk

P₁/p₂ = √3/1
Question 10
4 / -1

The equation of a wave is given by y = Asin ω(x/v-K) Where Asin ω is angular velocity and v is linear velocity. The dimension of K is

A
LT

B
T

C
T^-1

D
T²

Solution

Check the dimensional correctness -

L.H.S.=R.H.S.

- wherein

It is based on the principle of homogeneity. According to this principle both sides of an equation must be the same.

From principle of homogeneity (x/v) has dimension of T.