Kinetic Energy
What is kinetic energy?
Energy of an object in motion
What are the three types of potential energy?
Gravitational, chemical and elastic
What is work?
a force applied through a distance
What is a machine?
a device that change the force or increases the motion from work
How do we find Mechanical Energy?
KE + PE
How do we calculate kinetic energy?
KE = 1/2m x v2
What three quantities are needed to find gravitational potential energy?
mass, gravity, height
What is the unit for work and how do we calculate it?
J; F x d
List three simple machines
Lever, pulley, wheel, inclined plane, wedge, screw
What is energy?
The ability to cause change
Which quantity has the largest impact on kinetic energy?
velocity
A 4 kg celiling fan is placed 2.5 m above the floor. What is its GPE?
98J
How much work do you do when you lift a 100N child 0.5m?
50J
Can a machine increase both force and speed? Explain
No, some of the force applied to the machine will always be lost. It can never be 100% efficient.
According the Law of Conservation of Energy, what causes objects to slow down and lose energy?
Friction
A baseball with a mass of 0.15kg is moving at a speed of 40 m/s. What is the baseballs Kinetic energy?
120J
A 0.5 kg apple has a GPE of 0.75J. What is the height of the apple relative to the ground?
2m
Give an example of when no work would be done on an object.
Does not move, no force applied, the applied force is perpendicular to motion
If you decrease the input force and increase the input distance of a machine, what will happen?
Greater force over a smaller distance.
If you increase the amount of time a transfer of energy occurs, what will happen to the amount of power generated?
Power decreases
A jogger with a mass of 60kg is moving forward and has 270J of kinetic energy. What is the joggers velocity?
3m/s
Which would have a larger GPE, a 2,500 kg boulder 200m above the ground or a 1,000 kg buffalo 329m above the ground?
Boulder
How does the angle of a force applied and the direction of an object relate to work?
Larger angle means less work is done
How can you make a machine more efficient?
Reduce friction
You transform 950J of chemical energy into mechanical energy to push a sofa. If it took you 5 s to move the sofa, what was your power? What is the unit for Power?
190 W