ch. 4 - energy i. energy and work (p.100-123) energy work conservation of energy
DESCRIPTION
A. Energy Kinetic Energy (KE) energy in the form of motion depends on mass and velocity 80 km/h 50 km/h 80 km/h 80 km/h truck 50 km/h motorcycle Which has the most KE? Which has the least KE?TRANSCRIPT
Ch. 4 - EnergyCh. 4 - Energy
I. Energy and Work (p.100-123) Energy Work Conservation of Energy
A. EnergyA. Energy
ENERGY
motion of electric chargesbonding of atoms
motion of objects
internal motion of particles
changes in the nucleus
The ability to cause change.
MECHANICAL
ELECTRICALCHEMICAL
NUCLEAR
THERMAL
joules (J)
A. EnergyA. EnergyKinetic Energy (KE)
energy in the form of motion depends on mass and velocity
80 km/h
50 km/h
80 km/h
80 km/h truck
50 km/h motorcycle
• Which has the most KE?
• Which has the least KE?
A. EnergyA. EnergyPotential Energy (PE)
stored energy depends on position or configuration
of an object
• Which boulder has greater gravitational PE?
• What other ways can an object store energy?
B. WorkB. WorkWork
transfer of energy through motion force exerted through a distance
W = FdDistance must be in direction of force!
W: work (J)F: force (N)d: distance (m)
1 J = 1 N·m
B. WorkB. WorkBrett’s backpack weighs 30 N. How much
work is done on the backpack when he lifts it 1.5 m from the floor to his back?
GIVEN:F = 30 Nd = 1.5 mW = ?
WORK:W = F·dW = (30 N)(1.5 m)W = 45 J
FWd
B. WorkB. Work A dancer lifts a 40 kg ballerina 1.4 m in the air
and walks forward 2.2 m. How much work is done on the ballerina during and after the lift?
GIVEN:m = 40 kgd = 1.4 m - duringd = 2.2 m - afterW = ?
WORK:W = F·d F = m·aF =(40kg)(9.8m/s2)=392 NW = (392 N)(1.4 m)W = 549 J during liftNo work after lift. “d” is not in the direction of the force.
FWd
C. Conservation of EnergyC. Conservation of EnergyLaw of Conservation of Energy
Energy may change forms, but it cannot be created or destroyed under ordinary conditions.
EX: PE KE mechanical thermal chemical thermal
C. Conservation of EnergyC. Conservation of EnergyPE KE
View pendulum animation. View roller coaster animation.
C. Conservation of EnergyC. Conservation of EnergyMechanical Thermal
View rolling ball animations. View skier animation.