What Is Force?

Force can move an object or stop it

We use force to move an object and to stop it. For example, in baseball, when we hit the ball we use force to push it.  The catcher tries to grab the ball by using force to stop it.

Force can change the shape of an object

How many of you enjoy working with Play-Doh? It’s so much fun to make models by using your creativity isn’t it? Did you know that when you shape them, you are applying force? We use force to give various shapes to the dough. Thus, force can change the shape of an object too.

Friction

Now let’s say you kick a ball. Does the ball roll and stop after some time? Do you know that there is another type of force involved here? When the ball rolls, it rubs against the surface of the ground, which applies a force on the ball in the opposite direction. This force is known as FRICTION. When you kick the ball, it overcomes the friction for some time and moves forward but eventually, friction overtakes and stops the ball! Now let’s say, you move a ball on a rough surface and another one on a smooth surface with the same force. You will realize that the ball on the rough surface will stop first. This means that rough surfaces exert more force or friction that stops the ball earlier. There are three kinds of friction –

1) Air Resistance –

It’s the force on an object moving through air. It affects how fast or slowly an object can travel through it. The streamlined shape of a bird helps it to move faster as it minimizes the area of contact with air. On the other hand, a parachute uses its big surface area to slow down descent towards the ground.

2) Water Resistance –

The force on an object floating on or moving in water is called water resistance. The streamlined shape of ships, submarines and fishes helps them to move swiftly by minimizing the force of resistance on them.

3) Surface Resistance –

The force on an object moving across a surface, such as an ice-skater is known as surface resistance. The soles of our shoes, the tire treads of automobiles are designed in a way so as to optimize the grip with the ground to avoid slipping.

Mechanisms or Simple Machines can Reduce your efforts

Some tools or types of equipment such as levers, pulleys, and wheels can be used to turn a small force into a bigger force. They can help us accomplish tasks more easily. For example, levers help us lift great weights by giving us extra pull or push. Pulleys that comprise of wheels on an axle, along with ropes, are used to lift heavy objects with ease. A wheel reduces the friction by allowing the contact surfaces to roll rather than drag over each other. Other examples are screws and gears. Guess how they may help.

Check Point

1. Classify the following forces between contact and non-contact forces (field forces)

Muscular, Gravity, Friction, Magnetism

2. Name any two devices that help in minimizing the applied force to do an activity.
3. The ________ shape of fishes and airplanes help them to move in water and air respectively.
4. A parachute uses __________ to slow down their descent towards the ground.
5. An apple falling to the ground is an example of the force of _________.

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