Given Questions §

1.    What happens to the energy in a system if it is never destroyed? §

It changes form, energy cannot be destroyed due to the first law of thermodynamics.

2.    What other resource apart from energy can be extracted from oil? §

Oil is also used to create plastics.

3.    What is the difference between a finite and an infinite energy source? §

A Finite energy source will eventually be depleted, e.g. Fossil Fuels.

A Infinite energy source is one that either is so large that it’s depletion is beyond a reasonable time frame, e.g. the sun, or a resource that replenishes over time, e.g. Hydropower

4.    Describe the way that electricity is generated in a hydroelectric power station. §

Water is stored at a ‘high point’ aka a Resoivour, or a downhill lake. When energy is generated, water isl et down fro it’s high position, thereby converting it’s gravitational potential energy into Kinetic Energy as goes down. This water is then used to turn a turbine/water wheel, the rotation of the turbine converts the water’s kinetic energy into mechanical kinetic energy, which spins a rotor shaft inside the generator that produces electricity.

5. A weightlifter ‘snatches’ a dumbbell from the floor to arm’s length, a vertical height of 0.8 m. Calculate the mass of the dumbbell (in kg) if the minimum work done in lifting it is 1200 Nm. §

Rearranged to

6. 1.    If a buggy of mass 110 kg travels at 30 m/s, how much kinetic energy does it possess? §

, therefore

7.    A crane raises a load of 200 kg a height of 30 m in one minute at uniform speed. Determine the kinetic energy of the load when it is moving. §

given , Kinetic energy involves Mass and Velocity, = 0.5 Mass = 200kg (from source)

8.    Calculate the potential energy available from a reservoir holding 3800 litres of water at a height of 280 m. (1 litre of water has a mass of 1 kg.) §

Given , potential energy involes mass, given by the litres, gravity, given by earth (9.8m/s), and a height, given by 280m therefore

9. A portable electrical generator can deliver energy at a rate of 8 kJ per second. Calculate the current that can be drawn from the generator if the electricity is supplied at a voltage of 220 volts. §

Given |

10. Calculate the heat energy required to heat 12 kg of water from a temperature of 15 ºC until it begins to boil. §

= 4284000J or 4284kJ

11. If an electric light bulb uses 75 kJ of energy in 12 minutes, what is the power rating of the bulb? §

= 104.16

Other Questions §

Bagge of weight 20kg goes up a conveyor belt at a slope of 3.5m, calculate the potential energy when it is at the top

A 12 Volt car battery has a capacity rating of 35 amp hours (it can supply a current of 35 amps for 1 hour, or 5 amps for 7 hours, or any other cobination giving an equivalance of 35 amp hours) Determine the amount of electrical energy the battery can supply.