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When you place your palm in front of a moving ball and then remove your palm, what happens to the speed of the ball?
What happens to the speed of the ball when children compete to move a rubber tyre by pushing it?
Application of force always results in a change in the state of motion of an object.
False
What is the force that enables us to perform activities involving movement or bending of our body?
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In digestion, the food gets pushed through the alimentary canal with the help of ___.
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What is atmospheric pressure?
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How is atmospheric pressure demonstrated through the example of the rubber sucker?
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Why couldn't Otto von Guericke's hemispheres be pulled apart by horses?
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To draw water from a well we have to __________ at the rope.
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The north pole of a magnet __________ the north pole of another magnet.
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What force brings a moving ball to rest on the ground?
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What is the direction of the force of friction on moving objects?
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Friction between water and a boat brings the boat to a stop only when rowing stops.
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A magnet can exert a force on another magnet without being in ______ with it.
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Match the force with its type:
- Friction
- Magnet
- Electrostatic
- Gravity
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What is the force that pulls objects towards the Earth?
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Define pressure in terms of force and area.
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What is a force?
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How can the speed of an object change when a force is applied?
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To move an object, does it have to be pushed or pulled?
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A force can be larger, smaller, or equal in __________ to another force.
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Match the following situations with the correct action: (a) Moving a loaded cart, (b) Opening a drawer, (c) Drawing a bucket of water from a well
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Study Notes
Force and Motion
- Force is a push or pull that can cause an object to change its motion or shape.
- Everyday experiences involve forces, such as kicking a ball, pushing a cart, or opening a door.
- Forces can be grouped into two categories: push and pull.
Forces are due to Interaction
- A force is a result of the interaction between two objects.
- At least two objects must interact for a force to come into play.
- Examples of interaction include a man pushing a car, girls pushing each other, and a cow and a man pulling each other.
Exploring Forces
- Forces can be applied in different directions, such as pushing a heavy object from the same direction or from opposite directions.
- When two forces act in the same direction, they add up, and when they act in opposite directions, they subtract from each other.
- The strength of a force is expressed by its magnitude, and its direction must also be specified.
A Force can Change the State of Motion
- When a force acts on an object, it can change its speed or direction of motion.
- The net force acting on an object determines its effect on the object's motion.
- Examples of forces changing the state of motion include a football player kicking a ball, a goalkeeper trying to stop the ball, and a batsman playing a shot in cricket.
A Force can Change the Shape of an Object
- When a force is applied to an object, it can change its shape, such as pressing a lump of dough or squeezing a rubber ball.
- Forces can be applied in different ways, such as pressing, pulling, or lifting, to change the shape of an object.
- Examples of forces changing the shape of an object include pressing a spring, stretching a rubber band, and compressing a scale.
Types of Forces
- Muscular force is a type of force resulting from the action of muscles in our body.
- Muscular force enables us to perform various activities, such as pushing, pulling, lifting, and bending.### Forces and Their Effects
- A force is a push or a pull that can cause an object to change its motion or shape.
- Forces can make an object:
- Move from rest
- Change its speed
- Change its direction
- Change its shape
- A force can also bring an object to rest or stop it from moving.
Muscular Force
- Muscular force is a type of contact force.
- It is the force exerted by muscles in our bodies.
- Animals also use muscular force to perform various tasks.
- Examples of muscular force include:
- Lifting a book or a bucket of water
- Pushing or pulling an object
Contact Forces
- Contact forces are forces that require physical contact between objects.
- Examples of contact forces include:
- Muscular force
- Friction
- Normal force (force exerted by a surface on an object)
- Contact forces can be either push or pull forces.
Non-Contact Forces
- Non-contact forces are forces that do not require physical contact between objects.
- Examples of non-contact forces include:
- Magnetic force
- Electrostatic force
- Gravitational force
- Non-contact forces can also be either push or pull forces.
Friction
- Friction is a type of contact force.
- It is the force that opposes motion between two surfaces in contact.
- Friction can cause an object to slow down or come to rest.
- Examples of friction include:
- A ball rolling on the ground and slowing down
- A car's tires gripping the road
Magnetic Force
- Magnetic force is a type of non-contact force.
- It is the force exerted by magnets on other magnets or magnetic materials.
- Like poles of a magnet repel each other, while opposite poles attract each other.
Electrostatic Force
- Electrostatic force is a type of non-contact force.
- It is the force exerted by charged objects on other charged or uncharged objects.
- Like charges repel each other, while opposite charges attract each other.
Gravitational Force
- Gravitational force is a type of non-contact force.
- It is the force that attracts objects with mass towards each other.
- The force of gravity is what keeps us on the ground and what makes objects fall.
Pressure
- Pressure is the force exerted per unit area.
- It is calculated as force divided by area.
- Pressure is a scalar quantity.
- Examples of pressure include:
- The pressure of a nail on a wooden plank
- The pressure of air on the walls of a container
Pressure Exerted by Liquids and Gases
- Liquids and gases exert pressure on the walls of their containers.
- The pressure exerted by a liquid or gas depends on the height of the column and the area of the container.
- Examples of pressure exerted by liquids and gases include:
- The pressure of water in a pipe
- The pressure of air in a balloon
Atmospheric Pressure
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Atmospheric pressure is the pressure exerted by the air in the atmosphere.
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It is a type of non-contact force.
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The pressure of the atmosphere is what keeps us on the ground and what makes it difficult to pull a sucker off a surface.### Changes in Motion
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A change in the speed of an object or the direction of its motion or both implies a change in its state of motion.
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Force acting on an object may cause a change in its state of motion or a change in its shape.
Types of Forces
- Contact force: force that acts on an object by being in contact with it
- Non-contact force: force that acts on an object without being in contact with it
- Muscular force: force exerted by muscles
- Gravitational force: force that attracts objects with mass towards each other
- Magnetic force: force that attracts or repels magnetic poles
- Frictional force: force that opposes motion between two surfaces in contact
Pressure
- Pressure: force per unit area
- Liquids and gases exert pressure on the walls of their containers
- Atmospheric pressure: pressure exerted by air around us
Examples of Forces
- Push and pull: examples of contact forces that change the state of motion of objects
- Archery: example of muscular force, contact force, and gravity
- Squeezing lemon: example of muscular force, contact force, and shape change
- Taking out toothpaste: example of muscular force and contact force
- Blacksmith hammering: example of force changing the shape of an object
- Inflated balloon: example of electrostatic force and attraction
- Plastic bucket: example of gravitational force, normal force, and atmospheric pressure
- Rocket launch: example of gravitational force and thrust force
- Dropper: example of atmospheric pressure and pressure of water
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Description
This quiz covers the concept of force and pressure learned in Class 7, including how to determine the motion of objects and the effects of force on distance and direction.
