4 2 work power and energy resources

Work done is the product of the force applied to an object and the distance over which the force is applied, measured in joules (J).

False. Work is done when a force is applied to an object and results in the object's movement over a distance in the direction of the force.

The formula for calculating work done is Where:

False. Work can also be done electrically, by heating or by radiation.

True. The amount of energy transferred (in joules) is equal to the work done (in joules) when any mechanical work is done.

The relationship between energy transferred and work done is:

True. Work is done on a ball when it is lifted to a height.

Gravitational potential energy is the energy transferred to an object due to its change in height in a gravitational field.

False. Energy is transferred to an object's gravitational potential store when it is lifted.

False. Gravitational potential energy is measured in units of joules (J).

In the gravitational potential energy equation, represents the mass of the object in kilograms (kg).

The equation for calculating gravitational potential energy is Where:

In the gravitational potential energy equation, represents the gravitational field strength in newtons per kilogram (N/kg).

False. Energy is transferred away from an object's gravitational potential store when it falls.

Kinetic energy is the amount of energy an object has as a result of its mass and speed.

True. Any object in motion possesses kinetic energy.

The equation for calculating kinetic energy is Where:

False. Kinetic energy is measured in units of joules (J).

In the kinetic energy equation, represents the speed of the object in meters per second (m/s).

In the kinetic energy equation, represents the mass of the object in kilograms (kg).

If an object has a mass of 2 kg and a velocity of 5 m/s, then it has 25 J of kinetic energy.

True. Energy transfers can be assumed to be perfect (100% efficient) if the wasted energy is negligible.

True. The energy transfers in a pendulum can be equated as . This kind of energy equivalence is used in lots of calculations involving kinetic and gravitational potential energy.

Power is the rate at which energy is transferred or work is done, measured in watts (W).

False. Power refers to the rate at which energy is transferred or work is done, not the total amount of energy transferred.

False. A car has more power if it does the same amount of work in a shorter amount of time.

The formula for calculating power is:
Where:

The rate of doing work, or power, refers to the amount of work done or energy transferred per unit time. It is measured in watts (W).

False. Power is the rate at which energy is transferred or work is done, work done is the total amount of energy transferred.

False. Power is typically measured in watts (W), while energy is measured in joules (J).

Solar cells, also known as photovoltaic cells, are devices made of semiconducting materials that produce electricity from sunlight.

True. Solar energy is considered renewable because it is derived from the Sun which is expected to continue shining for billions of years.

Solar panels are devices that transfer energy from sunlight to the thermal store of the panels, which is then used to heat water.

The three main fossil fuels are:

Wave and tidal power stations generate electricity by utilising the motion of waves or tides to turn turbines, which then generate electricity through electromagnetic induction.

The main purpose of underwater turbines in wave and tide power systems is to transfer energy from the kinetic store of the moving water to the kinetic store of the turbines, which turn generators that generate electricity.

Hydroelectric dams are structures built across rivers to store water at a height in reservoirs. The water can be released, flowing over a turbine that turns a generator that generates electricity.

Geothermal energy is energy stored in the thermal store of rocks beneath the Earth's surface from tectonic heating. The hot rocks are used to heat water that can be used as a hot water supply and to produce steam to turn turbines for electricity generation.

False. Geothermal energy is considered a renewable resource.

False. Solar panels produce no greenhouse gases or pollution once they are operating.

False. Burning fossil fuels produces carbon dioxide which is a greenhouse gas that contributes to global warming. But other harmful gases are also released in the combustion of fossil fuels, such as sulphur dioxide which causes acid rain.

Advantages of solar energy include:

The main advantage of hydroelectric dams is their ability to respond to electricity demand quickly and reliably.

The main advantages of biofuels are:

True. Nuclear power stations do not release pollution into the atmosphere during normal operation.

False. Solar farms need to be large-scale to produce significant amounts of electricity.

The disadvantages of using fossil fuels include:

The primary advantages of wave and tide power are that they are renewable energy resources that produce no pollution.

The main disadvantage of hydroelectric dams is that they require valleys to be flooded. This results in the destruction of habitats, towns, and villages.

The primary advantage of geothermal energy is its reliability and renewability. It offers a consistent source of heating and electricity production.

The main disadvantage of geothermal energy is the limited availability of suitable locations for large-scale electricity production.