science ( forces / energy )

• A force is something that causes an object to change its speed, direction or shape
• a object can exert a force on another object through physical contact.
• friction is the force that opposes motion between two surfaces in contact.
• elastic force is the force acting on a stretched or compressed elastic to return to its original shape.
• gravitational force is the force that attracts two objects towards each other.
• a planet exerts such a force on the objects on it and pulls them towards the center, this is called weight
• magnetic force is the force exerted between a magnet and another magnetic object.
• unlike poles attract, like poles repel.
• weight is hence a type of force and is measured using SI unit of newton.
• mass is the amount of matter in an object, it is measured as kilograms/kg.
• weight is measured using a spring balcance, it works by stretching a spring when a force is exerted on it.
• when we lift or push an object, we are doing work because we are moving that object against gravity.
• the more mass something has, the greater its weight will be.
• mass is measured using a beam balcance, it works by balancing the mass of an object with an equal mass on the other side of the balcance.
• the mass of an object will not change despite the change of location as the amount of matter does not change.
• the weight of an object will change as gravitational force on the object changes when its location changes.
• when two or more objects interact, they exert a force on one another, this results in a transfer of energy causing changes in motion or rest.
• a force can move a stationary object, change the speed of an object, change the direction an object is moving to and stop a moving object.
• a force applied on an object can cause a turning effect about a fixed point called a pivot.
• the transfer of energy between objects can cause changes in size or shape of an object.
• pressure is an effect of force acting on an object, it is affected by the amount of force exerted on it and the area contact between two objects.
• pressure = force / area
• the pressure is greater when we go deeper underwater.
• by sucking on a straw, we remove some air and lower the air pressure in the straw.
• by pressing on a suction cup, air is pushed out and the air pressure between the cup and the surface decreases.
• work is done when a force is applied, an object moves and it moves in the same direction as the force applied on it.
• fossil fuels are formed from the remains of dead plants and animals, such fuels are limited and non-renewable
• the burning of fossil fuels releases air pollutants and greenhouse gases into the environment, contributing to air pollution.
• greenhouse gases contributes to global warming and increases the rate of climate change.
• solar panels are made of materials that capture sunlight and converts light energy to electric energy.
• hydroelectric energy is electrical energy that is generated by turbines when moving water powers them.
• a hydroelectric power station stores water in a reservoir behind a dam and water is then released and the moving water turns turbine to generate eletricty.
• wind energy covert energy from the wind to eletrical energy.
• wind turbines take up a lot of space and can destroy the natural habitats of wildlife. birds can also be killed if they fly into turbines. lastly, turbines can be very noisy and produces noise pollution.
• biofuels is made from animal waste or plant materials, they can also be produced by recycling food waste.however, the burning of it can also pollute the environment. biofuels is used to power vehicles.
• nuclear, solar, wind, hydroelectric, geothermal and biofuel energy is clean energy.