Science - Physics Y7

Forces

A force is a push, pull or a twist. They cause a change in somethings motion or shape. A force can start something moving, speed it up, stop something moving or slow it down.

Newtons (N)

The word Newton refers to how forces are measured, newtons are the amount of force is used on the object measured using a spring balance.

Resultant Force

Resultant force is representing the combined effect of multiple individual forces acting upon an object. They could both be acting upon the same direction or opposite, allowing the stronger force in the opposite direction to move the object in that direction.

Balanced Force

When two forces working in opposite directions are the same strength resulting in no change in motion

Unbalanced Forces

When two forces working in opposite directions are not the same strength resulting in a change of motion in the object

Mass

Mass is the amount of matter in an object which never changes and is measured in (kg, g, tonne)

Weight

Weight is the pulling force of gravity which changes wherever you are and is measured in (Newtons). The weight of an object would be different on different planets due to different amounts of gravity.

Gravity

Gravity is a pulling force of attraction between you and everything around you. It is also a non-contact force as it doesn’t require physical touch to pull objects down.

Gravitational Pull

All objects that have mass have its own gravitational pull, the bigger the mass the bigger gravitational pull.

Gravitational Field

A region around a mass where another mass experiences a force of attraction due to gravity.

Friction

Friction is a contact force that opposes motion between two objects in contact. It slows objects down and happens due to small bumps on every surface of every object. When the two surfaces rub against each other, the bumps catch and grab on to each other resulting in friction.

Good Friction

Walking (you push your foot backwards against the ground which pushes you forwards), if there is no friction like on ice, then you will slip and you need friction to pick things up, walk, run, ride a bicycle, etc.

Bad Friction

Friction between two objects can wear away at the surface of an object, making it weaker and thinner. Friction between an object and air acts to slow the object down resulting in air resistance or drag.

Increasing Friction

You can make friction stronger by using rough surfaces, pressing objects together harder, or using materials that create more grip. Other ways to increase friction include making the object heavier or changing the texture of its surface.

Decreasing Friction

Reducing friction make machines run more efficient, cheaper to run and more longer lasting. Using wheels on a trolley, people can wheel around heavier objects instead of sliding it across the ground, lubricants such as oil reduce the friction between moving parts, for example in a motor

Simple Machine

A device that makes work easier (Lever, Wedge, Screw, Wheel and axle)

Lever

A lever is a simple machine made from a long, rigid object, A lever has a point about which it rotates- this is called the fulcrum, Most levers increase the size of the effort that you can apply, making the job easier

Mechanical Advantage

The ratio of output force to input force