Transcript Energy and Work Section 10.1

Energy and Work
Section 10.1
Physics
Objectives
Describe the relationship btwn work
and energy.
Display an ability to calculate work
done by a force.
Identify the force that does work.
Differentiate btwn work and power
and correctly calculate power used.
Energy
Energy: the ability of something to
produce change in itself or the
environment.
Energy can come in many forms:
– Thermal Energy.
– Chemical Energy.
– Potential Energy.
– Kinetic Energy.
Energy
Kinetic Energy: Energy of motion.
To find kinetic energy
mathematically, there is one main
equation:
– KE = ½ (m)(v²)
– Kinetic energy equals one half mass
times velocity squared.
Energy and Work
Energy and work are related.
Energy is used to do work.
Work: The process of changing the
energy of the system.
Ex. Raking leaves.
– System: you and raking leaves.
– Chemical energy is changed into kinetic
energy to rake the leaves.
Work
W = Fd
– Work equals force times distance.
– The relationship between doing work
and a resulting change in energy, W =
ΔK.
– Work-Energy Theorem: founded by
James Prescott Joule.
– Energy is measured in Joules: J.
Work
Can work be done on an object such
as a brick wall?
No. The object on which the force is
applied must move through a
distance!
Practice Problems
Page 227.
1-5.
Forces at an Angle
W = Fd
If a force is applied at an angle, the
components need to be calculated.
Fx = F (cos Θ)
Fy = -F (sin Θ)
Or to find the work:
– W = Fd (cosΘ)
Practice Problems
Page 229.
6-8.
Power and Work
Power is the rate of doing work.
P = W/t
– Power equals work divided by time.
Practice Problems
Page 231.
9-12.