Forces and energy

What are the types of forces?

non-contact force and contact force.

What is a contact force?

A force acting between two objects is in physical contact with each other.

What is the SI unit of force?

N (newtons)

What is a scalar quantity?

A number quantity that has a MAGNITUDE, UNIT

LIKE,

Time,

Mass,

Volume,

Temperature,

Angle,

Distance,

Speed,

Light,

Intensity,

Loudness,

Energy,

Density

What is a vector quantity?

A numerical quantity that has a MAGNITUDE and a UNIT, DIRECTION

Velocity,

Acceleration,

Displacement,

Force,

Weight (as weight is a force)

When the net force is zero, what is happening? (two situations)

The object is either NOT MOVING (STATIONARY, it is the better term), or it is moving at a constant velocity.

Forces should be drawn at? How is the CG found? (in uniformed objects). What is an exception?

THE CG. The CG is in the middle of an object. Use dotted lines to find it (not circles)

BUT, the frictional force is drawn at the area where the object meets a surface. (also it opposes motion)

(BTW, CG will divert towards a part of an object which is heavier)

Changes of gravitational field strength. (what changes it?)

The distance between the centre of a planet.

CLOSER TO CENTER OF EARTH (e.g, STRONGER GRAVITATIONAL FIELD STRENGTH.

FARTHER FROM THE CENTRE OF EARTH (e.g, WEAKER GRAVITATIONAL FIELD STRENGTH.

What is the effect of forces?

Move a stationary object

Change the speed of an object

Change the direction of an object

Stop a moving object

Change the shape or size of an object

What is pressure?

The amount of force acting on a specific area.

FORMULA=

P=N/SA (force/surface area)

Pressure is affected by?

Temperature

Force

Surface area

An example is in the sea. Deeper into the sea, more water is pushing onto you. This leads to an increase in force (increase of the weight of water pushing onto you), and this increases pressure.

Difference in pressure (example, suction cups)

I cant explain this well. But in terms of the suction cups,

• You push the air out of the gap between the suction cup and the surface.

• This creates a low-pressure area inside the suction cup because there’s less air trapped.

• Meanwhile, the atmospheric pressure outside the suction cup remains higher.

• Since atmospheric pressure is greater than the pressure inside, it pushes the suction cup firmly against the surface.

• This pressure difference holds the suction cup in place.

When is work done?

When an object moves in the same direction as the force applied.

What happens when work is done?

a transfer of energy will occur

How is work calculated?

Work done is calculated by the force in newtons applied times the distance travelled in the same direction as the force in meters.

What is the unit for work done?

J (joules)

What value is work?

A scalar value, meaning it has NO negatives.

Types of energy sources

Fossil fuels

Solar energy

Hydroelectric energy

Wind energy

Geothermal energy

Biofuels

What are fossil fuels?

Fuels that are formed from the remains of dead plants and animals buried in the Earth millions of years ago.

What is the impact of fossil fuels on the environment?

It releases air pollutants like greenhouse gases that lead to global warming and an increased rate of climate change

What impact does solar energy have on the environment?

It has a minimum impact during the process of harnessing solar energy.

HOWEVER, during the process of production or disposal of solar panels, toxic waste may be generated.

What are the impacts of hydroelectric energy?

It has a minimum greenhouse gas production in the process of harnessing energy.

BUT, flooding in the area behind the dam can kill plants, and cause animals and humans to relocate, which can affect human livelihood

Wind energy’s impact on the environment

Requires a large plot of lands to build farms which may result in a loss of wildlife as natural habitats are destroyed.

Geothermal energy’s impact on the environment

Requires large areas of land, which may affect the natural habitats of wildlife and the diversity of species

They may also draw out traces of toxic elements from underground.

What are biofuels?

Fuels made from animal waste/plant matter that cannot be eaten by humans or produced from the recycling of food waste such as cooking oil and plant pulp

How is biofuel used?

Ethanol is produced from plants to power motor vehicles

Biofuel’s impact on the environment

Releases air pollutants like carbon dioxide into the atmosphere.

Advantages of biofuel

When plants are grown to make biofuel, they take in carbon dioxide and help balance the amount of carbon dioxide released into the atmosphere.

Plants that are grown to make biofuel can be grown quickly.

Biofuels can also be made from food waste, and help recycle and reduce waste.

Nuclear energy’s impact to the environment

Risk to health and safety for those living near a nuclear plant and we need to dispose nuclear waste too.

Advantages of nuclear energy

Clean energy (no air pollutants produced) and requires less land compared to others

Energy conversion of fossil fuels

Chemical potential energy (fossil fuel) → Heat energy (water) → kinetic energy (turbine) → electrical energy (generator)

Energy conversion of solar energy

Light energy (the sun) → electrical energy (solar cell)

Energy conversion of hydroelectric energy

Gravitational potential energy (water stored behind a dam) → kinetic energy (water) → kinetic energy (turbine) → electrical energy (generator)

Energy conversion of wind energy

Kinetic energy (wind) → kinetic energy (wind turbine) → electrical energy (generator)

Energy conversion of geothermal energy

Heat energy (Earth’s core) → Kinetic energy (steam) → Kinetic energy (turbine) → Electrical energy (generator)

Energy conversion of biofuels

Chemical potential energy (biofuel) → heat energy (Steam) → kinetic energy (vehicle)

Energy conversion of nuclear energy

Nuclear energy (atoms) → heat energy → kinetic energy (turbine) → electrical energy (generator)