Work and Energy Flashcards
What is the formula for work?
Work = Force × Distance
What are the units of work?
Joules (J) or Newton-meters (Nm)
What is the relationship between energy and work?
Energy is the capacity to do work; work and energy are equivalent.
What is Gravitational Potential Energy (GPE), and what is its formula?
GPE is the energy an object has due to its height. Formula: GPE = mgh
How can GPE be increased?
By increasing mass or height.
What is Kinetic Energy (KE), and what is its formula?
KE is the energy due to motion.
Formula: KE = ½ m v²
What are some other forms of energy?
- Elastic potential energy (due to change in shape)
- Chemical energy (stored in chemical compounds)
- Thermal/Heat energy (lost due to friction)
- Nuclear energy (from radioactive elements)
- Solar energy (from the Sun’s light)
- Electric energy (due to charges)
What is the law of conservation of energy?
Energy cannot be created nor destroyed, only transformed from one form to another
How can we calculate velocity when only given height?
v = √(2gh)
What happens to kinetic energy when an object hits the ground?
- If it stops immediately, all KE is lost as heat and sound.
- If it rebounds, some KE is lost as heat and sound.
How does air resistance affect energy?
Some energy is lost as heat and sound due to friction with air.
How is energy converted in a pendulum?
- At the highest points: All energy = GPE
- At the lowest points: Energy = KE + GPE
How does friction affect a moving bicycle?
Some energy is lost as heat due to friction, reducing the KE at the lowest point.
What is power, and what is its formula?
Power is the rate of doing work.
* Power = Work / Time
* Power = Energy / Time
* Power = Force × Velocity
What are the units of power?
Watts (W) or Joules per second (J/s)
What is efficiency, and how is it calculated?
Efficiency is the ratio of useful output energy to input energy.
* Efficiency = (Useful Output Work / Input Energy) × 100%
* Efficiency = (Useful Output Power / Input Power) × 100%
How can we improve efficiency?
- Increase useful output energy
- Reduce wasted energy
- Use less input for the same result
What are common examples of fossil fuels?
Coal, natural gas, oil, and petrol.
What is one advantage of using fossil fuels for electricity?
They provide a high output of energy and can generate electricity continuously.
What are two disadvantages of fossil fuels?
They are non-renewable and cause pollution (including acid rain and global warming).
How do nuclear fuels generate electricity?
Through nuclear fission, which produces heat to create steam that drives a turbine connected to a generator.
Name one advantage of nuclear power.
It offers a very high output of energy and continuous generation of electricity.
Name one disadvantage of nuclear power.
It requires strict safety measures and produces dangerous nuclear waste.
Which energy sources typically use thermal power stations?
Fossil fuels and nuclear fuels.
How do thermal power stations produce electricity?
They burn fuel or use nuclear reactions to boil water, producing steam that turns a turbine connected to a generator.
How is geothermal energy converted to electricity?
Water is heated by hot rocks deep underground, creating steam that drives a turbine and generator.
Give two advantages of geothermal energy.
It is renewable and has no direct fuel costs.
Give two disadvantages of geothermal energy.
Limited suitable locations and the high cost/difficulty of deep drilling.
How do hydroelectric and tidal power stations generate electricity?
They use the potential energy of water (falling or tidal) to drive turbines connected to generators.
What is one advantage of hydroelectric or tidal power?
They are renewable and have no fuel costs.
What is one disadvantage of hydroelectric or tidal power?
They can be expensive to build and may cause environmental damage.
How is wind energy converted into electricity?
The kinetic energy of moving air turns turbine blades, which drive a generator.
Name one advantage of wind energy.
It is clean, renewable, and has no fuel cost.
Name one disadvantage of wind energy.
It provides relatively low output and requires a large, consistently windy area.
How do solar panels generate electricity?
They convert sunlight (light energy) directly into electrical energy.
What is one advantage of solar energy?
It is renewable, clean, and requires no fuel cost.
What is one disadvantage of solar energy?
It depends on weather/sunlight availability and can be expensive
How can wave energy be used to produce electricity?
The kinetic energy of ocean waves can drive turbines connected to generators.
Why is wave energy not widely used?
It’s often less efficient, location-specific, and can be technologically challenging or expensive.
How does biomass generate electricity?
The chemical energy in organic materials (like wood or waste) is released by burning, producing steam to drive a turbine and generator.
What is the difference between renewable and non-renewable energy sources?
Renewable sources do not run out (or can be used repeatedly), while non-renewable sources are finite and eventually deplete.
Which power station does not use any moving parts to generate electricity?
Solar panels
Name three energy sources that do not originate from the Sun.
Nuclear fission, geothermal, and tidal.
What is linear momentum, and what is its formula?
Momentum is mass × velocity. Formula: P = m × v
What are the units of momentum?
kg·m/s
How do we calculate the change in momentum?
- If momentum is in the same direction: ΔP = mv - mu
- If momentum is in opposite directions: ΔP = mv + mu
How is force related to change in momentum?
F = ΔP / t or F = m (v - u) / t
What is impulse?
Impulse is equal to change in momentum (ΔP) or Force × Time of contact
What does the law of conservation of momentum state?
Total momentum before a collision = Total momentum after a collision
What are the types of collisions?
- Elastic collision: KE is conserved (m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂)
- Perfect inelastic collision: Objects stick together; KE is lost (m₁u₁ + m₂u₂ = v(m₁ + m₂))
How does conservation of momentum apply to rockets?
Before launch, momentum is zero. When fuel burns, it produces downward momentum equal to the rocket’s upward momentum, making the rocket lift off.
How does conservation of momentum apply to a rifle and bullet?
When a bullet is fired forward, the rifle recoils backward with equal but opposite momentum.
How is efficiency defined in energy systems?
Efficiency is the ratio of useful output energy (or work) to the input energy, expressed as a percentage:
* Efficiency = (Usefuloutputenergy / Inputenergy)×100%
What is the relationship between impulse and momentum?
Impulse, defined as force multiplied by the time of contact (Impulse = F × t), equals the change in momentum of an object (ΔP). Momentum is a vector quantity given by mass times velocity.
