Kinetic Energy
What is the formula for kinetic energy?
The formula for kinetic energy is KE=1/2 m v2
m is mass and v is velocity.
What is the formula for gravitational potential energy?
The formula for gravitational potential energy is PE=mgh,
where m is mass, g is the acceleration due to gravity, and h is height.
What is efficiency in the context of energy transfer?
(you can provide the equation)
Efficiency is the ratio of useful energy output to total energy input, expressed as a percentage.
useful energy x 100
Total input
What does the slope of a speed-time graph represent?
The slope of a speed-time graph represents acceleration and deceleration
What does a steep slope on a distance-time graph indicate?
A steep slope indicates a high speed.
If a car with a mass of 1000 kg is traveling at a speed of 20 m/s, what is its kinetic energy?
KE=1/2×1000×(20)2=200000 J.
If an object weighs 10 kg and is lifted to a height of 5 m, what is its gravitational potential energy?
PE=10×9.8×5=490 J.
How do you calculate efficiency?
Answer the question - a lightbulb takes in 500J of energy
It releases: 200J of light, and 300J of heat
Efficiency can be calculated using the formula
Efficiency=(Useful Output EnergyInput Energy)×100Efficiency=(Input EnergyUseful Output Energy)×100.
200/500 x 100 = 40%
If a speed-time graph shows a horizontal line, what does this indicate about the object's motion?
A horizontal line indicates that the object is moving at a constant speed (no acceleration).
How can you identify a stationary object on a distance-time graph?
A stationary object is represented by a horizontal line on the graph.
How does increasing speed affect the kinetic energy of an object?
Kinetic energy increases with the square of the speed, meaning small increases in speed result in large increases in kinetic energy.
How does height affect gravitational potential energy?
Gravitational potential energy increases with height;
the higher the object, the greater the potential energy.
If a machine does 500 J of work with an energy input of 1000 J, what is its efficiency?
Efficiency=(500/1000)×100=50%.
How can you determine the acceleration from a speed-time graph?
Acceleration can be determined by calculating the slope of the line on the graph.
change in speed over change in time
How can you find the average speed from a distance-time graph?
Average speed can be found by dividing the total distance by the total time taken, which can be determined from the graph.
Calculate the kinetic energy of a 1500 kg vehicle moving at 30 m/s.
Answer: KE=1/2×1500×(30)2=675000 J
KE=1/2×1500×(30)2=675000 J.
Describe how gravitational potential energy converts to kinetic energy during a free fall.
As an object falls, its energy changes from Gravitational Potential Energy to Kinetic Energy
Why is it important to maximize efficiency in energy systems?
Maximizing efficiency reduces energy waste, lowers costs, and minimizes environmental impact.
Bob and Ranbir decided to compare their acceleration when driving. Bob went from 3m/s to 8m/s within 5 seconds, whilst Ranbir went from 10m/s to 20m/s in 5 seconds. What was their acceleration? Who accelerated at a faster rate?
5m/s/5s = 1m/s2 - Bob
10m/s/5s = 2m/s2 - Ranbir
Ranbir had a greater rate of acceleration
What does a positive slope on a displacement-time graph represent?
A positive slope indicates that the object is moving in a positive direction (away from the starting point).
When an object is in motion
Calculate the gravitational potential energy of an object weighing 20 kg at a height of 10 m.
PE=20×9.8×10=1960 J.
If there are two lightbulbs taking in 2000J of energy. Lightbulb A releases 1700J of light and 300J of heat. Whilst Lightbulb B releases 1500J of light and 500J of heat. What is their efficiency and which one is the most efficient?
A - 85%, B - 75%, Lightbulb A is more efficient
Describe how to analyze a speed-time graph to find the total distance traveled by an object.
The total distance traveled can be found by calculating the area under the speed-time graph.
How can you tell if an object is moving backwards on a displacement-time graph?
A negative slope indicates that the object is moving backwards.