Physics Test 113

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Physics Test 113

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Weekly Quiz Competition

Question 1
4 / -1

In a rocket of mass 1000 kg fuel is consumed at a rate of 40 kg/s.The velocity of the gases ejected from the rocket is 5 x 10⁴ m/s.The thrust on the rocket is

A
2 x 10³ N

B
2.5 x 10⁴ N

C
2 x 10⁶ N

D
2 x 10⁸ N

Solution

Thurst = 5 x 10⁴ x 40

= 2 x 10⁶ N.
Question 2
4 / -1

Which of the following statements is false ?

A
force of friction is independent of mecroscopic area of the surface in contact

B
force of friction depends on the nature of materials of the surfaces in contact(i.e., force of adhension)

C
force of friction does not depends on the relative velocity between the surfaces

D
force of friction is independent of roughness or smoothness of the surfaces in contact

Solution

F = uN

which depends on roughness.
Question 3
4 / -1

A man walks over a rough surface; the angle between force of friction and the instantaneous velocity of the person is

A
π

B
π/2

C
2π

D
zero

Solution

Force is directed along the direction of motion.
Question 4
4 / -1

A heavy uniform chain lies on a horizontal table top. If the coefficient of friction between the chain and the table surface is 0.25, then the maximum fraction of the length of the chain, that can hang over one edge of the table is

A
20 %

B
25 %

C
35 %

D
15 %

Solution

nL×100/(1+n)L =25/1.25 =20%
Question 5
4 / -1

A particle is projected along the line of greatest slope up a rough plane inclined at an angle of 45° with the horizontal. If the coefficient of friction is 1/2, their retardation is

A
g/2

B
g/√2

C
g/2√2

D
3g/2√2

Solution
Question 6
4 / -1

A ball thrown vertically upward returns to its starting point in 4s. Its initial speed is

A
23.6 m/s

B
6 m/s

C
19.6 m/s

D
zero

Solution

V = u + at

o = u - 9.8x2

u = 19.6
Question 7
4 / -1

A stone is dropped from a certain height which can reach the ground in 5 second. If the stone is stopped after 3 second of its fall and then allowed to fall again, then the time taken by the stone to reach the ground for the remaining distance is

A
2 sec

B
3 sec

C
4 sec

D
None of these

Solution
Question 8
4 / -1

A stone is projected upwards from the top of a building with some initial speed and reaches the ground in 5sec. Now it is allowed to fall with the same initial speed downwards and reaches the ground in 3 sec. If the stone is allowed to fall freely under gravity from the same point, it will reach the ground in

A
4 s

B
2 s

C
15 s

D
8 s
Question 9
4 / -1

The position of a projectile is given by x = v₀t - Kt² where v0 equals 250 m/s and t is measured in seconds. Given that the velocity of the projectile falls to a value of 150 m/s at t = 5s. The value of the K is

A
5ms^-2

B
10ms^-2

C
20ms^-2

D
50ms^-2

Solution

x = Vot - Kt²

v = V₀ - 2kt

150 = 250 - 2k x 5

= k = 10.
Question 10
4 / -1

The two ends of a train moving with a constant acceleration pass a certain point with velocities u and v. The velocity with which the middle point of the train passes the same point is

A
(u + v)/2

B
(u² + v²)/2

C
[(u² + v²)/2]^1/2

D
(u² + v²)^1/2

Solution

Let the length of the train be ‘L’.

As it crosses the point, the initial velocity can be taken as ‘u’ and final velocity as ‘v’.

So, v² = u² + 2aL

=> v² – u² = 2aL ……………(1)

Suppose the velocity with which the midpoint crosses that certain point be v^/. In this case the distance traveled is L/2.

So,

(v^/)² = u² + 2a(L/2)

=> (v^/)² = u² + ½ × (v² – u²) [using (1)]

=> (v^/)² = (v² + u²)/2

=> v^/ = {(v² + u²)/2}^1/2

This is the velocity of the midpoint of the train with which it crosses that point.

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Re-Attempt Weekly Quiz Competition

Physics Test 113

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Physics Test 113

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SHARING IS CARING

Question 1

2 x 103 N

2.5 x 104 N

2 x 106 N

2 x 108 N

Solution

Question 2

force of friction is independent of mecroscopic area of the surface in contact

force of friction depends on the nature of materials of the surfaces in contact(i.e., force of adhension)

force of friction does not depends on the relative velocity between the surfaces

force of friction is independent of roughness or smoothness of the surfaces in contact

Solution

Question 3

π

π/2

2π

zero

Solution

Question 4

20 %

25 %

35 %

15 %

Solution

Question 5

g/2

g/√2

g/2√2

3g/2√2

Solution

Question 6

23.6 m/s

6 m/s

19.6 m/s

zero

Solution

Question 7

2 sec

3 sec

4 sec

None of these

Solution

Question 8

4 s

2 s

15 s

8 s

Question 9

5ms-2

10ms-2

20ms-2

50ms-2

Solution

Question 10

(u + v)/2

(u2 + v2)/2

[(u2 + v2)/2]1/2

(u2 + v2)1/2

Solution

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2 x 10³ N

2.5 x 10⁴ N

2 x 10⁶ N

2 x 10⁸ N

5ms^-2

10ms^-2

20ms^-2

50ms^-2

(u² + v²)/2

[(u² + v²)/2]^1/2

(u² + v²)^1/2