3. Work Work Work –Work is done on an object when a force is applied and it moves in a direction that is parallel to the force acting on it.

4. Unit for Work is the Joule Work = Force x Displacement Work = Force x Displacement JouleNewtonMeter Nmkg m/s 2 m Work is only done on an object if the force is parallel to the object’s displacement.

5. Work = F x cosine Θ x D

7. Energy Energy is the ability to do work. Energy is expressed in Joules. Work and energy are interrelated. –Work must done on an object to get to it move. –Moving objects can do work.

8. Positive and Negative Work –Positive work is done on object when it moves in the same direction in which the force is exerted. The speed of the object increases. –A student pushes back on the sidewalk to increase the speed of his skateboard. –Negative work is done on an object when the force opposes the forward motion of the object. The speed of the object decreases. –A student uses the brake on his roller blades to slow down.

9. Kinetic Energy Kinetic energy is the energy of motion. –It can be calculated by using the following equation. KE = ½ mv 2 Joule = kg x (m/s) 2 Joule = kg x (m/s) 2 N = kg m/s 2 x m N = kg m/s 2 x m Nm = Joule Nm = Joule If the object’s mass is doubled then the kinetic energy is doubled but it the velocity is doubled the kinetic energy is quadrupled!

11. Potential Energy Potential energy is stored energy. –Anytime a particle or object is forced to maintain a position in which it would not naturally exist has potential energy. –This natiral position is known as equilibrium. Types of Potential Energy –Gravitational Potential Energy –Elastic Potential Energy –Electrical Potential Energy –Chemical Potential Energy

12. Elastic Potential Energy The energy stored in an elastic material

13. Elasticity Elasticity is the ability of a material to return to its original shape after being deformed. –F = kx F = Force (N) k = spring constant (N/m) x = amount spring or material is stretched or compresses. (m) – a negative x means the spring is compressed –A positive x means the spring is stretched.

14. Elastic Potential Energy The amount of elastic energy stored in a spring. –E e = ½ kx 2 expressed in Joules – E e = elastic potential energy k = spring constant x = degree spring is stretched or compressed x = degree spring is stretched or compressed

15. Gravitational Potential Energy PE = mgh mass x 9.8 m/s 2 x height mass x 9.8 m/s 2 x height

16. Work Energy Theorem Work causes a change in kinetic energy. Work = Δ energy W = ½ mv 2 final - ½ mv 2 initial W = ½ mv 2 final - ½ mv 2 initial Slowing down or increasing the speed of an object changes its kinetic energy. A force must be applied and thus work must be done to change the kinetic or potential energy of and object.

18. Power Rate in which work is done. Power is expressed in Watts – Watts = Joules/second – 1 horse power = 740 W