GSEB Solutions for Class 7 Science and Technology – Motion, Force and Speed

GSEB Solutions for Class 7 Science and Technology – Motion, Force and Speed (English Medium)

GSEB SolutionsMathsScience
Exercise 65:          

Solution 1(a):

Exercise 66:

Solution 1(a):

The following objects are in motion:

1. A train in motion.
2. A swaying slide.
3. The hands of a wall clock.
4. The blades of an electric fan
5. Wings of a flying bird.

Solution 1(b):

No, the motion of each object is not the same. There is a difference in motion of different objects. Some objects perform linear motion, while some perform random motion; some perform circular motion, while some perform oscillatory motion. Thus, we can say that different objects perform different type of motion.

Solution 1(c):

The following are some examples of linear motion:

1. Motion of a bicycle moving on a straight road
2. Motion of a bullet fired from a gun
3. Motion of light rays
4. Motion of a fruit falling from a tree

Solution 1(d):

The following are some examples of circular motion:

1. Motion of a merry-go-round
2. Motion of a farmer’s sling
3. Motion of the blades of a fan
4. Motion of the Earth revolving around the Sun
5. Motion of a spinning top

Solution 1(e):

The following are some examples of uniform circular uniform motion:

1. Motion of the hands of a clock
2. Motion of the Earth around the Sun
3. Motion of the Earth around its own axis

Exercise 66:

Solution 1(a):

The following are some examples of periodic motion:

1. Motion of the hands of a clock
2. Motion of the Earth around the Sun

(Note: Periodic motion can be circular motion and oscillatory motion)

Solution 1(b):

The following are some examples of curved motion:

1. Motion of smoke arising from an incense
2. Motion of a flying mosquito
3. Motion of snake moving

Solution 1(c):

A moving bicycle performs random motion. The wheels of the bicycle perform circular motion.

Solution 1(d):

1. Linear motion
2. Circular motion
3. Circular motion
4. Oscillatory motion
5. Circular motion as well as periodic motion
6. Periodic motion
7. Oscillatory motion
8. Circular motion
9. Periodic motion as well as circular motion
10. Random motion

Exercise 68:

Solution 1(a):

The small car is behind the passenger bus initially. But, in the second picture the car is in front of the passenger bus. Thus, we can say that the speed of the car is highest amongst the three vehicles.

Exercise 70:

Solution 1(a):

The pair D had the maximum speed because the pair had taken the least time to cover the same distance. Thus, an object which takes lesser time to cover the same distance travels with more speed.

Solution 1(b):

The pair E had maximum speed because the pair travels the maximum distance in the same time. Thus, an object which travels a greater distance in same time will have more speed.

Solution 1(c):

The other possible units of speed are centimeter/second or kilometer/hour.

Solution 1(d):

Distance travelled by Vijay on bicycle = 300 m
Time taken = 60 s
We have to find the speed of the bicycle.

Exercise 71:

Solution 1(a):

Distance travelled by Shruti = 100 m
Time taken = 8 s
We have to find the speed of Shruti

Thus, Shruti’s speed of running is 12.5 m/s.

Solution 1(b):

Force was applied to move the tables in the classroom.

Solution 1(c):

We apply force for many activities in our day to day life. Some of them are as follows:

1. To perform all our daily morning routine activities.
2. In running and doing exercise
3. To lift our school bag
4. While  walking to school
5. To lift a bucket
6. To water the plants
7. To hit the ball with a bat or throw a ball while playing cricket
8. To move an object like a book kept on table
9. To open or close a drawer
10. To kick a soccer ball, etc.

Exercise 72:

Solution 1:

The ball starts moving and set in motion from the state of rest.

Solution 2:

The speed of the ball increases.

Solution 3:

The direction of the moving ball changes.

Solution 4:

The rolling ball stops moving.

Solution 5:

Yes. The shape of the balloon changes.

Exercise 73:

Solution 1(a):

In our day to day life, muscular force is used for performing the following activities:

1. To lift a school bag
2. To ride a bicycle
3. To move a table
4. To climb staircase
5. To board a bus or a train

Exercise 74:

Solution 1(a):

In our day to day life gravitational force is useful in the following activities:

1. Fruits falling down to the ground
2. Jumping in a swimming pool
3. Sliding down a slide
4. Standing erect on the floor

Exercise 75:

Solution 1(a):

A person slips, when he/she steps on a banana skin. A person can walk easily due to friction between the surface of the road and soles of the feet. If the surface becomes smooth, the frictional force decreases. As the banana skin is slippery, when one steps on it, the frictional force necessary to walk is not produced. So, a person slips if he/she steps on a banana skin.

Solution 1(b):

When brakes are applied to a moving vehicle, frictional force is produced between the brakes and the rim of the vehicle. This reduces the speed of the vehicle and its motion is retarded.

Solution 1(c):

When vehicles move, friction is produced between the tyres of the vehicles and the ground. Due to friction, wear and tear is caused in the tyres of the vehicles. Hence, we need to change the tyres of our vehicles after sometime.

Solution 1(d):

When we walk, frictional force is produced between the sole of our shoes and the ground. The soles of the shoes wear and tear due to friction. Hence the soles of the shoes wear out after prolonged use.

Exercise 76: