Force and movement

A force is a push or a pull.

Watch this video to learn about force and movement

A force is a push or a pull of an object.

If a push or a pull is applied to a book on your desk, we say force has acted on the book whether the book changed its position or not.

The harder you push or pull an object the greater the force you use.

This means we apply more force on heavier objects than on lighter ones.

Gravity is an example of a force because it pulls objects downwards towards the earth.

Similarly friction is a force because it acts in the opposite direction that force is applied.

Friction opposes motion.

### Units of force

Force is measured in Newtons.

The symbol for Newtons is N.

Force can be measured using a spring balance.

1 Kg is equal to 10N

## Friction

Friction is a force that opposes motion.

Friction acts between two surfaces that are in contact or that move over each other. e.g. the book on the table.

When you rub your hands together you feel some resistance that is caused by friction.

If you continue rubbing your hands rapidly then you will feel some heat or warmth in your hands.

This is an effect of the force of friction.

Friction has both advantages and disadvantages in our daily lives.

### Advantages of friction

• Friction makes a pen write.

• Friction helps us in walking.

• Friction helps in stopping moving objects for example cars.

• Friction helps in lighting a match.

### Disadvantages of friction

• It wears down moving parts of a machine

• It produces heat, which may be harmful and not required in a process.
• It wears out shoes.

There is more friction between the shoes and the grass than the snow and the snowblades.

The wheel in contact with road exhibits rolling friction.

### Increasing friction

Force of friction can be increased by:

• Increasing the force between the two surfaces that are in contact by increasing the weight of the objects.

• Increasing the roughness of the two surfaces that are in contact. e.g. in sand paper,files

## Friction can be reduced by

• Oiling or greasing (lubricating) the moving parts or the surfaces that are in contact.

Oil or grease is applied to the hinges of doors and windows to reduce friction.

Engines and machines are lubricated with oil to reduce friction.

• Using rollers between the moving parts.

• Using ball bearings between the moving parts.

• Reducing force between the moving parts.
• Making the two surfaces in contact be as smooth as possible.
• By separating the contact surfaces by an air cushion e.g., a hovercraft, can travel over rough land, swamp or sea.

### Sources

• force_3 by elimu used under CC_BY
• force_reaction_and_gravity by elimu used under CC_BY
• force_reaction_book by elimu used under CC_BY
• forces_balanced by elimu used under CC_BY
• force_small by elimu used under CC_BY
• Friction_force_book by elimu used under CC_BY
• Friction_matches by elimu used under CC_BY
• Friction_matches by elimu used under CC_BY
• movement_640_24f by elimu used under CC_BY
• Spring_balance by elimu used under CC_BY
• force_newton by elimu used under CC_BY
• Newton_force_weight by elimu used under CC_BY
• Spring_balance by elimu used under CC_BY
• force_friction_1 by Unknown used under CC_BY-SA
• force_friction_hands by Wordpress used under CC_BY-SA
• force_friction_pen by elimu used under CC_BY
• force_friction_walking by elimu used under CC_BY
• force_friction_walking by elimu used under CC_BY
• force_friction_wheel_movement by elimu used under CC_BY
• Friction_matches by elimu used under CC_BY
• force_friction_gear by TheSamba.com used under CC_BY-SA
• force_friction_wheel by TutorVista.com used under CC_BY-SA
• force_friction_worn_out_shoes by well dressed dad used under CC_BY-SA
• forces_friction_on_snow_and_grass by Mr zimmerman's class used under CC_BY-SA
• force_friction_file by Edited used under CC_BY-SA
• force_friction_loads by Amusing planet used under CC_BY-SA
• force_friction_sandpaper by Edited used under CC_BY-SA
• force_friction_bearing by Craftsman used under CC_BY-SA
• force_friction_hovercraft by 10 themes wallpapers used under CC_BY-SA
• force_friction_oiling_1 by indian mart used under CC_BY-SA
• force_friction_oiling_2 by instructubles used under CC_BY-SA
• force_friction_rollers_2 by school for champions used under CC_BY-SA
• force_friction_rollers by INDUSTRIE.com used under CC_BY-SA
• Force_friction_quiz by Unknown used under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License

• All work unless implicitly stated is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.