ICSE Living Science Physics for Class 6 Solutions Chapter 3 Force
Check Your Progress 1 (Page 36)
Answer the following.
Question 1.
What do you understand by a force ?
Answer:
Force is a push or pull acting upon an object as a result of its interaction with another object.
Question 2.
Give an example of a contact force.
Answer:
A person lifting a suitcase.
Question 3.
State another name for non-contact forces.
Answer:
Action-at-a-distance forces.
Question 4.
Define weight.
Answer:
The gravitational force acting on an object is called the weight of the object.
Question 5.
How will two oppositive charged objects behave with each other when brought close ?
Answer:
Oppositely charged objects attract each other when brought close.
A. Tick the most appropriate answer.
Question 1.
Which of the following is not an effect of force ?
a. Change in the direction of an object
b. Change in the shape and size of an object
c. Change in the mass of an object
d. Change in the position of a stationary object.
Answer:
c. Change in the mass of an object
Question 2.
Which of the following is a contact force ?
a. Graviational force
b. Frictional force
c. Electrostatic force
d. Magnetic force
Answer:
b. Frictional force
Question 3.
Cutting a piece of paper with a pair of scissors is an example of
a. applied force
b. frictional force
c. gravitational force
d. electrostatic force
Answer:
a. applied force
Question 4.
If two forces of 25 N and 15 N act simultaneously on an object in opposite directions, then the resultant force acting on the object will be
a. 40 N
b. 10 N
c. 15 N
d. 25 N
Answer:
b. 10 N
Question 5.
A charged ruler attracts bits of paper due to
а. gravitational force
b. magnetic force
c. electrostatic force
d. contact force
Answer:
c. electrostatic force
Question б.
Fill in the blanks.
Question 1
………….. is the SI unit of force.
Answer:
Newton is the SI unit of force.
Question 2.
Magnetic force is a ………… force.
Answer:
Magnetic force is a non-contact force.
Question 3.
The force acting on a mango falling from a tree is an example of ………….
Answer:
The force acting on a mango falling from a tree is an example of gravitational force.
Question 4.
Gravitational force is always …………………. in nature.
Answer:
Gravitational force is always attractive in nature.
Question 5.
A force acting on an object has both magnitude as well as …………..
Answer:
A force acting on an object has both magnitude as well as direction.
C. Match the following.
| Column A | Column B |
| 1. non – contact force | a. perpendicular to surface |
| 2. Catapult | b. an act of push or pull |
| 3. Force | c. unit of force |
| 4. Normal force | d. action-at-a-distance forces |
| 5. Newton | e. contact force |
Answer:
| Column A | Column B |
| 1. non – contact force | d. action-at-a-distance forces |
| 2. Catapult | e. contact force |
| 3. Force | b. an act of push or pull |
| 4. Normal force | a. perpendicular to surface |
| 5. Newton | c. unit of force |
D. State if the following statements are true or false.Correct the statement if it is false.
Question 1.
If two forces acting in opposite directions on a body are of equal magnitude, then the body will not move.
Answer:
True
Question 2.
Gravitational force is a contact force.
Answer:
False. Gravitational force is a non-contact force.
Question 3.
Like charges always attract each other.
Answer:
False. Like charges always repel each other.
Question 4.
It is possible that a force applied to an object may not bring any change in it.
Answer:
True
Question 5.
Two equal and opposite forces acting on an object balance out each other.
Answer:
True
Question 6.
Force applied on an object can increase its mass. False. Force applied on an object cannot increase its mass. Friction always acts in the direction of motion of an object.
Answer:
False. Friction always acts in the direction opposite to the direction of motion of an object.
E. Answer the following in a word or two or in a sentence.
Question 1.
Give an example in which a force can change the direction of an object.
Answer:
A moving bicycle changes its direction when a force is applied to steer its handle.
Question 2.
Which force is responsible for supporting the weight of a book placed on a table ?
Answer:
Normal force (contact force)
Question 3.
Which type of force acts on a string pulled from both ends ?
Answer:
Tension (contact force)
Question 4.
Name the force that is responsible for the falling of a stone from a height to the ground.
Answer:
Gravitational force
Question 5.
What do you understand by magnetic force ?
Answer:
The force of attraction that results between a magnet and another object is called magnetic force.
Question 6.
Why does a rolling ball stop after moving some distance?
Answer:
Due to frictional force acting on it which resists/opposes the motion of the object.
F. Answer the following in short.
Question 1.
Define force. Write its SI unit.
Answer:
A push or pull acting upon an object as a result of its interaction with another object is called force. Its SI unit is newton (N).
Question 2.
What will happen to an object if two equal forces act on it in opposite directions ?
Answer:
It two equal forces act on an object in opposite direction, they balance out each-other and the object does not move in any direction.
Question 3.
What do you understand by normal force ?
Answer:
A force exerted by a surface to support the weight of a body in contact with it is called normal force. It is always perpendicular (right angles) to the surface. For example, when a book is kept on a table, the table exerts a normal force which acts upward on the book to support its weight.
Question 4.
Why does a charged balloon stick to a wall ?
Answer:
It is due to the electrostatic force betwen the balloon and the wall. Opposite charges attract each other.
Question 5.
Why is magnetic force considered as an action-at-a- distance force ?
Answer:
Magnetic force comes into play even when the magnet and other object (like iron) are kept at a distance and not in direct
contact with each other. Hence, magnetic-force is considered as an action-at-a-distance force.
G. Answer the following in detail.
Question 1.
What are the various effects of force ? State one example of each.
Answer:
Various effects of force :
1. A force can move a stationary object. Example : Pulling a suitcase on its wheels.
2. A force can stop a moving object. Example : A ball rolling on rough surface comes to rest after some time due to force of friction.
3. A force can change the speed of a moving object. Example: We can increase the speed of a moving swing, we apply a force (push) in the direction of motion to increase its speed.
4. A force can change the direction of a moving object. Example: A moving bicycle changes its direction when a force is applied to steer its handle.
5. A force can change the shape and size of an object. Example: When we make a chapatti, a small ball of dough is changed to a flat, circular shape of a much bigger size by applying a force with the help of a rolling pin.
Question 2.
Differentiate between contact and non-contact force. Support your answer with suitable examples.
Contact forces :
- These are forces which need a physical touch on the object to act upon it.
- These may or may not be natural forces.
- They cannot work from a distance.
- Its various types are applied force, normal force, tension, frictional force.
- Examples : Player kicking a ball, game of tug-of-war, rolling ball stops, itself, horse pulling a cart, etc.
Non-contact forces :
- These are forces which do not need a physical contact to act on an object.
- These are natural forces.
- They can work from a distance as well.
- Its various types are magnetic force, electrostatic force, gravitational force.
- Examples : Magnet attracting iron nails, mango falling from tree, charged plastic ruler attracts bits of diy-paper, etc.
Question 3.
List all the forces acting on a boy sitting on a chair with the help of a suitable diagram.
Answer:
The forces acting on a body sitting on a chair are – Gravitational force (non contact) acting downwards, F . Normal contact force of the chair acting upwards (Fnorm) Both the forces are opposite and equal and balance each other.
Question 4.
Why do all objects have a tendency to fall towards the centre of the earth ?
Answer:
Gravitational force exerted by the earth is very strong. This force attracts all objects on earth towards its centre.That is why all objects on earth have a tendency to fall towards the centre of the earth.
Question 5.
Differentiate between mass and weight of an object.
Answer:
Difference between mass and weight Mass and weight mean completely different things in physics. The amount of matter that an object contains constitutes its mass. The gravitational force acting on this mass is called the weight of the object.
Mass of an object always remains the same, while the weight of the object varies when it is subjected to different gravitational forces. For example, the weight of an astronaut on the earth is six times her/his weight on the moon as the gravitational force of the earth is six times more than the gravitational force of the moon. But the body mass of the astronaut remains the same in both places.
H. Identify the agent exerting the force, the object on which the force is acting and the effect of force in the following situations :
Question 1.
Squeezing out the juice from an orange.
Answer:
Agent exerting the force can be a machine (electric power) or human.
The object on which the force is acting is the orange.
The force is moving the orange md changing the shape of it.
Question 2.
Taking out ointment from a medicinal tube.
Answer:
Agent exerting the force is human fingers. The object on which the force is acting is the medicinal tube. The force is changing the shape of the tube and moving the oinment out of the tube.
Question 3.
A child jumping to a height.
Answer:
Agent exerting the force is the child himself (muscle of the child).
The object on which the force is acting is the child himself. The force is moving the child from a stationaiy object.
I. Solve the following numerical problems.
Question 1.
Two horses pull a cart in the same direction with a force of 500 N each. Find the resultant force acting on the cart.
Answer:
The horses pull in the same direction.
Therefore, the resultant force acting on the cart = sum of both the forces
= 500 N + 500 N = 1000 N
The resultant force of 1000 N will act in the same direction as the individual forces on die cart.
Question 2.
Two force of 12 N and 25 N act on a body to the left hand side, while another force of 35 N acts on it to the right hand side. Find the resultant of the forces.
Answer:
Total forces acting to the left = 12 N + 25 N = 37 N Force acting to the right = 35 N
The resultant force on the body = difference between the magnitude of the forces = 37N – 35N = 2N
The object will move in the direction in which the force of 37 N is being applied, i.e., the resultant force of 2 N will act to the left.
Question 3.
Two persons are pushing a car with a force of 30 N and 70 N in opposite directions. Calculate the resultant force and its direction.
Answer:
Force acting in one direction = 30 N
Force acting in opposite direction = 70 N
Resultant force = Difference between the magnitude of force
= 70 N – 30 N = 40 N ’
The car will move in the direction in which the force of 70 N is being applied. The resultant force of 40 N will act on the car.
Question 4.
The forces acting on a wooden block are shown in the figure given alongside. Find the resultant of the forces and the direction of the resultant force.
Answer:
Total forces acting downwards = 2N + 22N = 24 N Total forces acting upwards = 8N + 14N = 22N Resultant force = Difference between the magnitude of forces = 24N – 22N = 2N
The wooden block will move in the downward direction with the resultant force of 2N acting on it.
J. Draw neat labelled diagrams to depict the following.
Question 1.
Electrostatic force
Answer:
Question 3.
Gravitational force on an object
Answer:
Living Science Physics Class 6 ICSE Solutions