- Books Name
- Class-8 Science Book
- PathSet Publications
- CBSE Class 8
Force can Change of State of Motion:-
A change in either the speed of an object, its direction of motion, or both, is described as a change in its state of motion. A force may bring a change in the state of motion of an object.
Example: A fielder catches a cricket ball coming with great speed and brings it to rest.
Force can Change the State of Motion:
- Force applied to an object may change its speed.
- If the force applied to the object is in the direction of its motion, the speed of the object increases.
- If the force is applied in the direction opposite to the direction of motion, then it results in a decrease in the speed of the object.
- A change in either the speed of an object, its direction of motion, or both, is described as a change in its state of motion.
- Thus, a force may bring a change in the state of motion of an object
- State of motion: an object is described by its speed and the direction of motion.
- The state of rest is considered to be the state of zero speed.
- An object may be at rest or in motion; both are its states of motion.
- Many times, the application of force does not result in a change in the state of motion.
- An object is said to be in motion if it is moving at a certain speed in a particular direction.
- If the object is at rest, it means that it is not changing its position for an observing point. Hence it has zero speed.
- When the object starts moving it means that its position is being changed for an observation point.
- In order to move an object from one place to another, a force is required to bring that object in motion.
- Not only this, a force applied to an object can change its speed, bring it to rest, or even change the direction of its motion.
- It may bring a combination of these effects as well such as a change in direction of motion and change in the speed of the motion altogether.
- Hence we can say that force can change the state of motion of an object.
- Any object cannot move by itself or change its state of motion on its own without the application of force.
- However, it is not a case that this change of state of motion will take place every time with every kind of object. For instance, if a person tries to push a very heavy object such as a wall, it would not at all.
Force can Change of Shape of an Object:-
A force on an object may change its shape.
Example: Pressing an inflated balloon with two hands compresses the balloon.
Force can lead to change in shape:
An object cannot move by itself, it cannot change speed by itself, it cannot change direction by itself and its shape cannot change by itself.
Force can change the shape of an object
The shape of an object can be altered if some force is applied to it. Depending upon the magnitude of the force that is being applied and the rigidity of the object, the effect on its shape and size can be observed.
- The above examples show how the use of force in different ways can change the shape of the object.
- So we can say that forces can change the shape of an object.
Effects of Force
Let us now look at some of the characteristics of force
1. A force can change the size and shape of an object. For example – While playing with clay we can change the shape of clay by applying force with our hands. The shape of the rubber band changes when it is stretched.
2. A force can change the speed of a moving object. Force can slow down or completely stop a moving object. To do this we need to apply a force in a direction opposite to the direction of motion of the moving body.
3. A force can move an object which is at rest. For example – A stationary trolley or trolley which is at rest can be made to move by applying some force. So the motion of an object can be halted by suitable application of force.
4. A force can change the direction of motion of a moving object. For example – A football can change its direction by kicking it in a different direction.
Note – Change in the mass of an object is not an effect of force.