FORMS OF ENERGY What is Energy The ability

FORMS OF ENERGY

What is Energy? The ability to do work Energy is transferred by a force moving an object through a distance.

What Unit is Energy Measured in? joules J Remember that work was also measured in joules. 1 J = 1 kg*m 2/s 2

2 General Types of Energy Kinetic energy Potential energy

Kinetic Energy of motion Depends on the mass and speed of the moving object

Kinetic Energy KE = ½ m Mass in kilograms Speed in m/s Kinetic energy in J 2 v

KE Practice A 70. 0 kg man is walking at a speed of 2. 0 m/s. What is his kinetic energy? 2 KE = ½ m v

KE Practice A 70. 0 kg man is walking at a speed of 2. 0 m/s. What is his kinetic energy? KE=½ m v 2 KE=1/2 (70. 0)(2. 0) 2 First square the speed. Then multiply. ½*70. 0*4. 0=140 J Remember!!!The unit is part of the answer!

KE Practice A 50. 0 kg cheetah has a kinetic energy of 18, 000 J. How fast is the cheetah running? 2 KE = ½ m v

KE Practice A 50. 0 kg cheetah has a kinetic energy of 18, 000 J. How fast is the cheetah running? KE=½ m v 2 You are solving for v this time. √(2 KE/m) = v First multiply 2 * 18, 000. Then divide that number by 50. 0. Last, take the square root of that number.

KE Practice √(2 KE/m) = v First multiply 2 * 18, 000. Then divide that number by 50. 0. Last, take the square root of that number. √ 2*18000/50. 0= 27 m/s

Potential Energy Stored energy Objects position or shape give them potential energy.

Potential Energy PE=mgh M=mass and g=gravity so mg=weight Mass in kg On Earth g=9. 8 m/s 2 H=height Height in meters

PE Practice Suppose the diver at the top of a 10. 0 meter high diving platform has a mass of 50. 0 kg. Calculate her potential energy. PE=mgh

PE Practice Suppose the diver at the top of a 10. 0 meter high diving platform has a mass of 50. 0 kg. Calculate her potential energy. PE=mgh PE=50. 0*9. 8*10. 0 G is 9. 8 because we assume she is on Earth. Simply multiply through. PE=4900 J

PE Practice A skydiver with a mass of 68 kg is about to jump from an airplane. His potential energy is 3046781 J. What height is he jumping from? PE=mgh

PE Practice A skydiver with a mass of 68 kg is about to jump from an airplane. His potential energy is 3046781 J. What height is he jumping from? PE=mgh Solve for h. PE/mg=h 3046781/68*9. 8 Multiply the bottom numbers first. Then divide. H=4572 m