﻿ A body of mass 3 kg is under a constant force which causes a displacement s in metres in it, given by the relation , where t is in s. Work done by the force in 2 s is: | Motion in Straight Line

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# Motion in Straight Line

#### Multiple Choice Questions

11.

A particle covers half of its total distance with speed v1 and the rest half distance with speed v2. Its average speed during the complete journey is

• v1v/ v1 + v2

• 2v1v2/v1 + v2

• 2v12v22 / v12 + v22

• 2v12v22 / v12 + v22

2761 Views

12.

A conveyor belt is moving at a constant speed of 2 m/s. A box is gently dropped on it. The coefficient of friction between them is μ = 0.5. The distance that the box - will move relative to belt before coming to rest on it taking

g= 10 ms-2 is

• 1.2 m

• 0.6 m

• zero

• zero

855 Views

13.

A ball is dropped from  a high-rise platform at t=0 starting from rest. After 6s another ball is thrown downwards from the same platform with a speed v. The two balls meet at t= 18s. What is the value of v? (take g= 10 ms-2)

• 74 ms-2

• 55 ms-1

• 40 ms-1

• 40 ms-1

1022 Views

# 14.A body of mass 3 kg is under a constant force which causes a displacement s in metres in it, given by the relation , where t is in s. Work done by the force in 2 s is:

C.

If a constant force is applied on the object causing a displacement in it, then it is said that work has been done on the body to displace it.
Work done by the force  = Force x Displacement
or          W = F x s                            ...(i)
But from Newton's 2nd law, we have
Force  =  Mass x Acceleration
i.e.,       F = ma                                ...(ii)
Hence, from Eqs. (i) and (ii), we get

Hence, Eq (ii) becomes

We have given

737 Views

15.

A particle moves along a straight line OX. At a time t (in seconds) the distance x (in metres) of the particle from O is given by

How long would the particle travel before coming to rest?

• 24m

• 40m

• 56m

• 56m

782 Views

16.

The x and y coordinates of the particle at any time are x = 5t – 2t2 and y = 10t respectively, where x and y are in meters and t in seconds. The acceleration of the particle at t = 2 s is

• 0

• 5 m/s2

• -4 m/s2

• -4 m/s2

1927 Views

17.

A toy car with charge q moves on a frictionless horizontal plane surface under the influence of a uniform electric field $\stackrel{\to }{E}$ . Due to the force q $\stackrel{\to }{E}$, its velocity increases from 0 to 6 m/s in one-second duration. At that instant, the direction of the field is reversed. The car continues to move for two more seconds under the influence of this field. The average velocity and the average speed of the toy car between 0 to 3 seconds are respectively

• 2 m/s, 4 m/s

• 1 m/s, 3 m/s

• 1.5 m/s, 3 m/s

• 1 m/s, 3.5 m/s

18.

The radius of earth is 6400 km and g = 10 m/s2. In order that a body of 5 kg weight is zero at the equator, the angular speed is

• $\frac{1}{800}\mathrm{rad}/\mathrm{sec}$

• $\frac{1}{1600}\mathrm{rad}/\mathrm{sec}$

• $\frac{1}{400}\mathrm{rad}/\mathrm{sec}$

• $\frac{1}{80}\mathrm{rad}/\mathrm{sec}$

19.

A wheel rotates with constant acceleration of 2.0 radian/sec2 .If the wheel starts from rest the number of revolution it makes in the first ten second, will be approximately

• 32

• 24

• 16

• 8

20.

A stone is thrown with an initial speed of 4.9m/s from a bridge in vertically upward direction.It falls down in water after 2sec. The height of bridge is

• 24.7m

• 19.8 m

• 9.8 m

• 4.9 m