Then put in the numbers: 3000 N × 5 m =15 000 joules Formula first: Then put in the numbers: = 1500W = 1.5 kW A family car might develop a power of 50 kW, a racing car perhaps 500kW and a Moon rocket 1 00 000 MW. Calculating Potential Energy (PE) 1. Gravitational Potential Energy This weight-lifter is lifting a mass of 200kg, up to a height of 2 metres. The potential energy of his weights: So: gravitational PE = work done change in PE (joules) = weight (N) × change in height (m) But g weight (in N) = mass (in kg) × where g = 10ms-2 here on Earth. So: change in gravitational PE = mass × g × change in height (joules) (kg) (N/kg) (m) g has different values on other _______________________. 2. Elastic Potential Energy (strain energy) This is the kind of energy stored in a bow, or in a catapult, or in a spring in a Energy stored = work done to stretch the bow, so: Elastic energy = average force × distance (joules) (newtons) (metres) Example
Then put in the numbers: 3000 N × 5 m =15 000 joules Formula first: Then put in the numbers: = 1500W = 1.5 kW A family car might develop a power of 50 kW, a racing car perhaps 500kW and a Moon rocket 1 00 000 MW. Calculating Potential Energy (PE) 1. Gravitational Potential Energy This weight-lifter is lifting a mass of 200kg, up to a height of 2 metres. The potential energy of his weights: gravitational PE = work done So: change in PE (joules) = weight (N) × change in height (m) But weight (in N) = mass (in kg) × g where g = 10ms-2 here on Earth. So: change in gravitational PE = mass × g × change in height (joules) (kg) (N/kg) (m) g has different values on other _______________________. 2. Elastic Potential Energy (strain energy) This is the kind of energy stored in a bow, or in a catapult, or in a spring in a Energy stored = work done to stretch the bow, so: Elastic energy = average force × distance (joules) (newtons) (metres) Example
year_8_science_work_energy_and_power.docx