Motion Test

Result

Motion Test - 68

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Question 1
1 / -0

A body performing uniform circular motion in a horizontal plane has a constant

A
Velocity

B
Acceleration

C
Kinetic energy

D
Displacement

Solution
Question 2
1 / -0

Rajdhini express moves at a speed of $$150\ km/h$$. How long will it take to cover a distance of $$15\ km$$?

A
$$0.1\ h$$

B
$$1.125\ h$$

C
$$2.125\ h$$

D
$$3.125\ h$$

Solution

Given,
Speed $$v=150\ km/h$$
distance cover = displacement $$d=15\ km$$ (Assume express is not changing its direction)

$$Velocity\ (V)=\dfrac{Displacement\ (d)}{time\ (t)}$$

$$t=\dfrac dV=\dfrac{15}{150}=0.1\ hr$$

Time taken $$t=0.1\ hr$$ Option A
Question 3
1 / -0

The figure represents the velocity-time graph of body moving in a straight line. How much distance does it travel during the last 10 seconds?

A
20 m

B
100 m

C
50 m

D
200 m

Solution

Distance travelled in last $$10$$ sec, is $$d = velocity \times time$$, which is nothing but area under the curve between the limit $$t = 10s$$ to $$t = 20s$$
So, area of triangle is $$= \dfrac {base \times height}{2} = \dfrac {(20 - 10)\times 20}{2} = 100\ m$$
Hence, correct option is (B).
Question 4
1 / -0

A body moves with initial velocity $$10ms^{-1}$$. If it covers a distance of $$20m$$ in $$2s$$, then acceleration of the body is

A
Zero

B
$$10ms^{-2}$$

C
$$5ms^{-2}$$

D
$$2ms^{-2}$$

Solution

Suppose the acceleration is $$a$$ then using the second equation of motion, $$s=ut+\dfrac{1}{2}at^2$$
and putting $$t=2sec$$ and $$u=10m/s$$
we get $$20=10\times 2+a\times 2$$
or $$a=0$$ that is $$uniform $$ motion.
Question 5
1 / -0

For a particle in uniform circular motion:

A
both velocity and acceleration are constant

B
acceleration and speed are constant but velocity changes

C
both acceleration and velocity changes

D
Speed is constant

Solution
Question 6
1 / -0

Can a body have a constant speed but variable velocity?

A
Yes

B
No

C
May be

D
None of these

Solution

Yes if the body is travelling with uniform speed in a circular track its speed remains the same but the velocity is non-uniform as the direction of the body is changing every time.
Question 7
1 / -0

The velocity-time graph of a body is shown in Fig.4.116. The displacement of the body in 8 s is

A
9 $$m$$

B
12 $$m$$

C
10 $$m$$

D
28 $$m$$

Solution

Displacement = area under graph
$$Area=\quad 2\times 2+\dfrac { 1 }{ 2 } \left( 2+6 \right) \times 1+\dfrac { 1 }{ 2 } \times 1\times 6-\dfrac { 1 }{ 2 } +1\times 6-1\times 6+2\times 4$$
$$=4+4+3-3-6+8=10m$$
$$Area=10m=displacement \ in \ 8sec.$$
Question 8
1 / -0

Which of the following remains constant in UCM?

A
Speed

B
Kinetic energy

C
Angular speed

D
All of these

Solution

When a body is moving on a circular track with constant speed then the motion of an object is known as uniform circular motion. During this motion magnitude of velocity or speed is constant but the direction of motion changes with respect to time. The sense of rotation and speed is constant so the angular speed and kinetic energy of the object will also be constant.
Option D
Question 9
1 / -0

Speed is to velocity as:

A
Centimetre is to metre

B
Force is to torque

C
Velocity is to acceleration

D
Distance is to displacement

Solution

Speed and velocity are related in much the same way that distance and displacement are related. Speed is a scalar and velocity is a vector. Both have SI unit m/s
Displacement is measured along the shortest path between two points and its magnitude is always less than or equal to the distance. The magnitude of displacement approaches distance as distance approaches zero.
From this it is clear that Option D is the correct answer
Question 10
1 / -0

The following figure gives the movement of an object. Select the correct statement from the given choices.

A
The total distance travelled by the object is $$975\ m$$

B
The maximum acceleration of the object is $$2\ ms^{-2}$$

C
The maximum deceleration happened between $$25th$$ and $$85th$$ seconds

D
The object was at rest between $$10th$$ and $$15th$$ seconds

E
At $$40th$$ second, the speed of object was decelerating

Solution