NIOS Class 10 Motion and its Description Worksheet 9 Answers

This worksheet contains questions based on motion and its types, distance, displacement, speed and velocity

This post explains the answers of questions given in the worksheet including explanation, diagrams. These solutions will help you complete your assignments and TMA also.

NIOS Class 10 Science (212) Worksheet 9 Solutions

Q1. In your surroundings, you will observe that some things are in motion while others are at rest. Make a list of things which are in motion. Based on your observations; explain the concept of motion and distinguish between rest and motion.

Answer

Examples of things in motion

   1. Moving car on road

   2. A flying bird

   3. Flowing water in the river

   4. A rotating fan

   5.  A running boy

Examples of things at rest

   1. A building

   2.  A tree

   3. A book lying on the table

   4. A chair in the room

   5. An electric pole

 

Concept of motion

An object is said to be in motion if its position changes with respect to a fixed point in a given time.

An object is said to be at rest if its position does not change

Differences between motion and rest

Motion	Rest
An object in motion if it changes its position with respect to a fixed point in given time.	An object at rest if it does not change its position with respect to a fixed point in given time.

 

 Conclusion: Motion and rest are relative terms. An object may appear to be at rest with respect to one observer but in motion with respect to another.

 

Q2. Continue to Q1, further observe that all the things which are in motion have similar motion or not.

(a)    If yes, support your answer with reasons.

(b)    If no, explain different types of motions with examples from day-to-day life.

Answer

No, all things in motion do not have similar motion. Different objects move in different ways depending on path, direction and speed.

Example: - A car move in straight line; fan rotates around its axis and a pendulum swing to and fro.

Types of motions

    1.  Rectilinear motion

    2. Circular motion

    3. Oscillatory motion

    4. Rotational motion

    5. Random motion

  

    1. Rectilinear motion: Motion along a straight path is known as rectilinear motion. Example – motion of train or car.

    2. Circular motion: Motion in a circular path is known as circular motion. Example- rotation of fan, motion of moon around the earth.

    3. Oscillatory motion: A repeated motion to and fro about a fixed point is called oscillatory motion. Example- motion of pendulum, a child on a swing.

   4. Rotational motion: The motion of an object about its own axis is called rotational motion. Example - Rotation of earth. Spinning top.

   5. Random motion: This type of motion does not follow a particular path. Example- movement of flies or insects

So, these are the different types of motion.

 

Q3. Provide examples of different types of motion from your surroundings.

Answer

We have already learnt different types of motion in the previous question. Following are the examples of these motion-

    1. Rectilinear motion – Car moving on road, a person walking along straight path, arrow shot from a bow.

   2. Circular motion- motion of merry-go-round, blades of ceiling fan, whirling of stone tied to a string.

   3. Oscillatory motion – Movement of pendulum of clock, vibration of tuning fork

   4. Rotational motion- Earth’s rotation on its axis, spinning top.

    5. Random motion- Movement of particles in the air, movement of fish in water,

 

Q4. You started moving from your home at 9:00 am on a straight road and reached market 5 km away. Stayed there for approx. 2 hours and returned back to home. While returning you took a different root which is shorter than before i.e. 3.8km. Represent graphically Distance and displacement travelled by you during your visit. Differentiate between distance and displacement.

Answer

 

 Difference between distance and displacement

Distance	Displacement
Total path covered by an object	Shortest straight-line distance between initial and final points
Scalar quantity	Vector quantity
Always positive	Positive, negative or zero

Q5. Different types of motions are represented graphically as given below. Identify and explain following figures representing different motions of a moving object correctly.

Answer

These are the distance -time graph which represent the motion of an object. These graphs show different types of motions

    1.  Graph a -In this graph a straight line with a positive slope. The distance increases uniformly with time. The object moves in straight line at a constant speed so the graph represents uniform motion.

    2. Graph b – In this graph, a curve gets steeper with time. The distance increases more rapidly as time passes, the graph represents accelerated motion.

   3. Graph c- In this graph, a curve goes flat over time. The distance increases first but then slow down with time. The object slows down. This graph represents decelerated motion.

    4. Graph d- In this graph a horizontal straight line which shows distance remains constant over time, it means the object at rest. There is no motion.

 

Q6. Observe moving things in your surroundings and estimate their speed/velocity. Give explanation how does velocity differ from speed? Support your answer why velocity is a vector quantity, but not speed.

Answer

Moving things and their speed/velocity

   1. A car travels at 40km/h. The velocity depends on direction e.g. 40 km/h east.

    2. Bicycle travels at 15 km/ h north.

    3. Airplane travels at 800 km/h towards Delhi.

Difference between Speed and velocity

	Speed	Velocity
Definition	Distance covered per unit time	Displacement covered per unit time in specific direction
Formula	Speed= distance/time	Velocity = displacement/ time
Type	Scalar quantity	Vector quantity
Example	A car is moving 60 km/h	A car is moving 60 km/h east.

Why velocity is a vector quantity but speed is not

Velocity has both magnitude and direction so it a vector quantity but speed has only magnitude so it is scalar quantity.

 

Q7. If you and your friend ride a bicycle on the road, you will notice that at different times, the both bicycles are found at different positions. Note down five positions at five times interval for each

a). Plot position Time Graph for Uniform Motion

b) Plot Position Time Graph for Non- Uniform Motion

c)Calculate Velocity from Position Time Graph.

d) Calculate Distance travelled by you and your friend in 10 minutes.

e) Examine whose speed is more?

Answer

Suppose you and your friend ride bicycles. Different positions are given at different time.

 

 

Time(min)	Your position (m)	Friend’s position(m)
0	0	0
2	100	90
4	200	180
6	300	270
8	400	260
10	500	450

This table shows uniform motion.

a). Plot position Time Graph for Uniform Motion

 

b) Plot Position Time Graph for Non- Uniform Motion

c)Calculate Velocity from Position Time Graph.

Calculate velocity from graph

 Velocity = slope of position -time graph

For uniform motion- slope is constant

 

For you

 

For your friend

 

For non-uniform motion, velocity changes at each interval

d) Calculate Distance travelled by you and your friend in 10 minutes.

Uniform motion

You = 500 m

Your friend =450m

Non- uniform motion – sum of individual segments

 You-

   Distance = 80 +110 + 120 +140 +50 =500m

Your friend -

Distance = 70 +90 + 90 +130 +70 =450m

e) Examine whose speed is more

You  

Your friend

You are faster than your friend

Q8. The velocity-time graph below shows the motion of a man. Calculate –

a)     The distance covered by the cyclist in 20 second and 25 seconds.

b)    Its velocity

c)     Its acceleration

Answer

Velocity of man = 20m/s

Time interval= upto 25s

(a)      Distance covered

 Distanced covered = Area under the velocity- time graph

 Since it is a rectangle (constant velocity)

 

Distance = Velocity ×Time

In 20 second

d= 20 ×20 =400m

In 25 seconds

d= 20 ×25=500m

 

(b)     Velocity

   20m/s (constant) from the graph

(c)       Acceleration

  

 

Final velocity = 20m/s

Initial velocity= 20m/s

Change in velocity = final velocity – initial velocity

 

A= 0m/s

Motion is uniform so there is no change in speed.

Q9. Derive/explain different equations of motion.

Answer –

 

Derivation of equations of motion

Consider an object moving with uniform acceleration ' a'

Let

Initial velocity = u

Final velocity =v (after time t)

Displacement = s

Time =t

There is certain relationship between these quantities

First Equation of Motion

We know that

 

               

    So         ……9.1

This is called first equation of motion.

Second Equation of Motion

We also know that

Displacement = (Average velocity) × (Time interval)

We substitute  from equation 9.1

Simplifying

 ……..9.2

This is called second equation of motion

If the object starts from rest (u=0)

So we see that the displacement of an object undergoing constant acceleration is proportional to t², while an object with constant velocity, displacement is proportional to t.

Third Equation of Motion

We know that

  and

Now we multiply these two equations

Now we multiply both sides by 2

 …….9.3

This is third equation of motion

Q10. A boy starting from rest travels 40 m in first 4 s and 200 m in next 6 s. what will be the velocity after 7 s from the start.

Answer

Given values

U= 0 m/s

Displacement in first 4 s = s₁= 40m

Displacement in next 6 s = s₂ =200m

Find acceleration in first 4 s

Velocity after 4 s

 = 0 + 5 × 4 = 20m/s

Acceleration in next 6s

 200= 120+18a₂

 

Velocity after 7s

After 4s , in next 3s

 20+ 4.44×3 = 33.3m/s