Motion Test

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Motion Test - 50

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Weekly Quiz Competition

Question 1
1 / -0

A driver is driving his car along a road as shown in Figure. The driver makes sure that the speed-o-meter reads exactly 40 km/h. What happens to the velocity of the car from P to Q ?

A
Velocity remains constant

B
Velocity first increases then decreases

C
Velocity first decreases then increases

D
Nothing can be decided

Solution

Since the speed-o-meter of the car reads exactly 40 km/h speed. This means that speed of the car remains constant always. also, from P to Q, the car moves in a straight line i.e. direction of motion of car does not change. So, velocity of the car, which is speed and direction combined, from P to Q remains constant.
Question 2
1 / -0

In Fig. 2.8

A
Retardation is uniform

B
Velocity is decreasing with time

C
Beyond M, the body has negative velocity

D
All the above statements are correct

Solution

From the velocity-time graph, we can say that the velocity of the body is decreasing. Also, up to time M, its velocity is positive and beyond M, its velocity is negative.
Also, the slope of the velocity-time graph gives the acceleration of the body. Since the slope of the graph is negative and constant. So, the body has constant acceleration in the negative direction. In other words, the body is uniformly retarding.
Thus, option D is correct.
Question 3
1 / -0

A body cannot have a

A
zero speed and non-zero acceleration

B
non-zero speed and zero acceleration

C
constant velocity and a varying speed

D
constant speed and a varying velocity

Solution

Speed of body is magnitude of velocity. So if velocity is only changing direction then speed is constant.
But if speed is changing then velocity have to be varying.
When a body starts moving the incident when t=0 then it have zero velocity but some acceleration is there.
Object moving with constant velocity has zero acceleration but non zero speed.
So only option C is not possible.
Question 4
1 / -0

Which of the following decreases in motion along a straight line with constant retardation?

A
speed

B
acceleration

C
displacement

D
none of these
Solution
- Option A:
By first equation of motion,
$$v=u-at$$
Since it is retardation, then $$a \rightarrow negative$$
Let us assume the moving body has some initial speed $$u$$ in $$+x$$ axis.
So we can see, as time $$t$$ increases, final speed $$v$$ decreases.
So option A is correct.

Option B:
Acceleration can't decrease because it is given in the question itself that it is constant retardation, i.e, constant acceleration opposite in direction to the speed.

Option C:
Displacement will also keep on increasing towards $$+x$$ axis as long as final speed $$v$$ doesn't become zero.
Question 5
1 / -0

The slope of a distance-time graph of a moving body gives its

A
Speed

B
Displacement

C
Velocity

D
Acceleration

Solution

The speed can be determined from the slope of the Distance-time graph.
Slope = $$=\frac{rise}{run}
=\frac{distance}{time}$$
Question 6
1 / -0

A stone tied to a string is whirled in a circle. As it is revolving, the rope suddenly breaks.Then :

A
The stone flies off tangential to the circle of rotation

B
The stone moves radially inward

C
The stone moves radially outward

D
The motion of the stone depends upon its velocity

Solution

When a stone is going around a circular path, the instantaneous velocity of stone is acting as tangent to the circle. When the string breaks, the centripetal force stops to act. Due to inertia, the stone continues to move along the tangent to circular path. So, the stone flies off tangentially to the circular path
Question 7
1 / -0

Choose the incorrect statement:

A
the speedometer of a car measures its instantaneous speed

B
the velocity of a body is always greater than the speed of that body.

C
the position-time graph of a body moving with variable velocity is a curve.

D
velocity-time graph of a uniform motion is a straight line parallel to time-axis.

Solution

Velocity is a quantity that has magnitude as well as direction so it can be negative and positive but the speed is a quantity that does not have any direction but has magnitude, there is no chance of getting negative. so the speed is always positive. so velocity can never be greater than the speed (maximum it can be equal to the speed if it travel in a straight line where direction does not matters )
Because speed is distance upon time and velocity is displacement upon time
and displacement can never be greater than distance so velocity can never be greater than speed.
Remaining options are true .
Speedometer reads speed at an instant. Position -time graph for variable speed is a curve because speed (slope of position -time graph) is changing.
And velocity-time graph for uniform motion will be horizontal line parallel to time-axis as velocity is fixed and does not change with time.
Question 8
1 / -0

A body whose speed in a particular direction is constant :

A
must be accelerating

B
must be retarding

C
has a constant velocity in that direction

D
all the above

Solution

Speed with direction is called Velocity.
A body whose speed in a particular direction is constant means it has a constant speed and it has a particular constant direction . Hence it has a constant velocity in that direction.
Question 9
1 / -0

A truck running along a straight line increases its speed uniformly from 30 m/s to 60 m/s over a time interval 1-min. The distance travelled during this time interval is

A
900 m

B
1800 m

C
2700 m

D
3600 m

Solution

Here, $$\displaystyle a=\dfrac { v-u }{ t } =\frac { 60-30 }{ 60 } =0.5{ m }/{ { s }^{ 2 } }$$
and $$\displaystyle s=\dfrac { { v }^{ 2 }-{ u }^{ 2 } }{ 2a } =\dfrac { { \left( 60 \right) }^{ 2 }-{ \left( 30 \right) }^{ 2 } }{ 2\times 0.5 } $$
$$\displaystyle =2700m$$
Question 10
1 / -0

The SI unit for the resultant velocity is

A
m/s

B
km/s

C
cm/s

D
min/s

Solution

velocity is given by $$\dfrac{displacement}{time}$$
SI unit of displacement is meter and that of time is sec.
so SI unit of velocity is meter/sec.

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Re-Attempt Weekly Quiz Competition

Motion Test - 50

Result

Motion Test - 50

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Rank

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SHARING IS CARING

Question 1

Velocity remains constant

Velocity first increases then decreases

Velocity first decreases then increases

Nothing can be decided

Solution

Question 2

Retardation is uniform

Velocity is decreasing with time

Beyond M, the body has negative velocity

All the above statements are correct

Solution

Question 3

zero speed and non-zero acceleration

non-zero speed and zero acceleration

constant velocity and a varying speed

constant speed and a varying velocity

Solution

Question 4

speed

acceleration

displacement

none of these

Solution

Question 5

Speed

Displacement

Velocity

Acceleration

Solution

Question 6

The stone flies off tangential to the circle of rotation

The stone moves radially inward

The stone moves radially outward

The motion of the stone depends upon its velocity

Solution

Question 7

the speedometer of a car measures its instantaneous speed

the velocity of a body is always greater than the speed of that body.

the position-time graph of a body moving with variable velocity is a curve.

velocity-time graph of a uniform motion is a straight line parallel to time-axis.

Solution

Question 8

must be accelerating

must be retarding

has a constant velocity in that direction

all the above

Solution

Question 9

900 m

1800 m

2700 m

3600 m

Solution

Question 10

m/s

km/s

cm/s

min/s

Solution

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