The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 2 Motion and Force Important Questions ensure conceptual clarity.
Motion and Force Extra Questions and Answers Class 8 Basic Science Chapter 2 Kerala Syllabus
Motion and Force Class 8 Important Questions
Question 1.
SI unit of force is ……………………….
Answer:
newton(N)
Question 2.
A child is standing in a field. With respect to the ground, the child is in a state of ……………………. (rest / motion).
Answer:
rest
Question 3.
If a body in motion covers equal distance in equal intervals of time, the body is said to have ………………………….. (uniform speed / non uniform speed).
Answer:
uniform speed
Question 4.
Cheetah is the fastest animal on land. Its speed is given in different ways. Which among these is correct?
a) 25 metre per s
b) 25 m/s
c) 25 m/s2
d) 25 M/S
Answer:
b) 25 m/s
Question 5.
Examine the figure below.
A man starts from A and reaches D through the points B and C. Find the distance travelled from A to D.
Answer:
Distance travelled from A to D = 4 + 3 + 4 = 11 km
Question 6.
Motion of four different objects are stated below. Choose the odd one. Also state the reason for choosing it.
(A train starting from the station, A stone thrown up, The motion of a ball rolling down a hill, The motion of a coconut falling from a coconut tree)
Answer:
A train starting from the station.
Because the other three (stone thrown up, ball rolling down a hill, and coconut falling) move mainly because of gravitational force.
Question 7.
The moving parts of machines experience wear and tear. Why?
Answer:
Due to frictional force
Question 8.
The solid substance used as a lubricant is ………………………
Answer:
Graphite
Question 9.
Bearings are used in motor vehicles. Why?
Answer:
Because rolling friction is less than that of sliding friction.
Question 10.
Define the term streamlining?
Answer:
The method of reducing friction by changing the shape is called streamlining.
Question 11.
“Overspeed of vehicles result in accidents”
Write two messages to be written on an awareness board in your school premises to minimise road accidents.
Answer:
Speed thrills but kills, Don’t mix drink with drive, Better late than never, Wear helmets while driving motor cycles.
Question 12.
The paths of two cars are as shown below. Car A started from P and reached R through Q and car B started from P and reached R through S.
a) What is the total distance covered by the car A?
b) What is the total distance covered by car B?
Answer:
a) Total distance covered by car A = 500 + 600 = 1100 m
b) Total distance covered by car B = 400 + 600 = 1000 m
Question 13.
Analyse the table given below and find which force is felt in each situation.
| Situation | Force |
| A coconut falling from a coconut tree | Gravitational force |
| Magnet attracts an iron nail | …………a)…………. |
| Hammering a nail | ……………b)………….. |
Answer:
a) Magnetic force
b) Muscular force
Question 14.
A book on a table is in a state of rest.
a) Identify the reference body for the above statement?
b) Considering the Sun as reference body, the book is in a state of (motion/rest)
Answer:
a) Reference body: Table
b) With respect to Sun, the book is in a state of motion
Question 15.
The conversation between two students standing on the road side about a person inside a moving bus is given below.
Student 1 “That person is at state of rest”
Student 2 “No, he is in motion”
Explain the possibilities of the correctness of these statements based on the concept of a reference body.
Answer:
- Reference body: Bus
That person with respect to the bus: State of rest
Student 1 – Statement is correct - Reference body: Road
That person with respect to the road: State of motion
Student 2 – Statement is correct
Question 16.
A person starts from A, moves through B, C and reaches D in 30 s.
a) Calculate the distance.
b) Find out the speed.
Answer:
a) Distance covered from A to D = 10 + 10 + 10 = 30 m
b) Speed = \(\frac{\text { Distance }}{\text { Time }}\) = \(\frac{30 \mathrm{~m}}{30 \mathrm{~s}}\) = 1 m/s
Question 17.
a) Choose the appropriate reference body from the given list so that a passenger sitting in a moving train can said to be in motion, (train, Another passenger next to him in the train, objects outside the train)
b) What is meant by the term ‘reference body’?
Answer:
a) The correct reference body is: Objects outside the train
Because the passenger is moving when seen from outside the train.
b) The object taken to determine the state of motion or the state of rest of a body is called the reference object.
Question 18.
What is frictional force? Point out two disadvantages of friction in our daily life and suggest remedy for overcoming it?
Answer:
When a surface moves or tries to move over another surface, a parallel force is produced between them against their relative motion. This force is called frictional force.
- Difficulty to draw water from the well.
Remedy – Apply oil in the pulley. - Chains of bicyles sometimes does not move due to friction.
Remedy – Apply grease on it.
Question 19.
Figure shows a device used in motor vehicles.
a) Name the device.
b) How much time will it take for a vehicle to cover a distance of 90 km at 60 km/h rate?
Answer:
a) Speedometre
b) Speed = \(\frac{\text { distance travelled }}{\text { time taken }}\)
distance travelled = 90 km
speed = 60 km/h
Time taken = \(\frac{90}{60}\) = 1.5 h
Question 20.
Observe the depiction of the path taken by a person as he moves from A to C through B.
Find out his speed?
Answer:
Speed = \(\frac{\text { distance travelled }}{\text { time taken }}\)
distance travelled = 20 m + 60 m = 80 m
Time taken = 4 s + 6 s = 10 s
Speed = \(\frac{80}{10}\) = 8 m/s
Question 21.
Complete the table suitably.
| Measurement | Unit |
| Time | …………..a)………….. |
| …………..b)………….. | m |
| Speed | …………..c)………….. |
Answer:
a) s
b) Distance
c) m/s
Question 22.
Classify the following situations into contact and non-contact forces.
a) Applying break in a bicycle.
b) The earth revolving around the sun.
c) The speed of a ball rolling on ground is reduced.
Answer:
Contact forces
a) Applying brake in a bicycle
c) The speed of a ball rolling on ground is reduced.
Non-Contact force
b) The earth revolving around the sun.
Question 23.
The following figure is of a traffic sign board placed near school for road safety.
a) What does the board indicate?
b) A motor bike rider travels 180 km in 2 hours through the road near the school. Calculate his speed. Does he cross the speed limits as per Kerala Road Safety Rules.
c) Which is the device used to find the speed in vehicles.
Answer:
a) Speed limit around this school area is 30 km/h
b) Speed = \(\frac{\text { distance travelled }}{\text { time taken }}\) = \(\frac{180}{2}\) = 90 km/h
Yes, The bike travelled in overspeed,
c) Speedometer
Question 24.
Classify the following situations as contact force and non-contact force.
a) A magnet attracting a nail
b) Pushing a wall
c) An apple falling from an apple tree
Answer:
a) A magnet attracting a nail – Non-contact force
b) Pushing a wall – Contact force
c) An apple falling from an apple tree – Non-contact force
Question 25.
A child starts from A and reaches C through B in 1 s.
a) What is the total distance travelled by the child?
b) Calculate the speed of the child?
Answer:
Total distance travelled by the child = 4 m + 3 m = 7 m
Speed = \(\frac{\text { distance travelled }}{\text { time taken }}\) = \(\frac{7}{1}\) = 7 m/s
Question 26.
Why are airplanes and boats made in special shapes?
Answer:
Airplanes and boats are made in special shapes to reduce friction. Smooth, streamlined designs help them move easily through air and water, making travel faster and easier by decreasing the resistance they face.
Question 27.
Bus A covered 75 m in 5 s. Bus B covered 169 m in 13 s.
a) Which bus covered a greater distance?
b) Which bus has a higher speed?
Answer:
a) Bus B covered greater distance (169 m).
b) Speed of bus A = \(\frac{75 \mathrm{~m}}{5 \mathrm{~s}}\) = 15 m/s
Speed of bus B = \(\frac{169 \mathrm{~m}}{13 \mathrm{~s}}\) = 13 m/s
Bus A has higher speed.