Definitions Part 1
What is the definition of "mechanics"?
The study of motion!
What is the definition of "energy"?
The ability to do work!
What two things do you need in order for work to happen?
A change in position and an applied force!
What's an easy way to give yourself, or any object, more potential energy?
Raise yourself, or it, higher off the ground (stand on a chair, jump in the air, hold it higher up, etc.)
When we observed the motion of basketballs in different situations, what caused the basketball to roll down the parking lot (and almost into the street)?
Gravity pulling it down the slope of the hill!
What is the definition of "potential energy"?
Energy that is being stored!
What is the definition of "kinetic energy"?
Energy that is being used!
Which is a better lubricant, sand or water?
Water! Remember a lubricant is substance made of molecules that easily slide past each other.
What would happen to a toy car if a pushed it (and got it moving) in a world with no friction?
It would just keep going until it hit something! Even then, it would bounce off and keep going until it hit something else.
In class, I rolled a single marble into a row of five marbles on a textbook. When the marble collided with the five marbles, the last marble on the very end started rolling away (similar to a Newton's cradle). Why?
The momentum from the first marble rolling transferred to the second marble which transferred to the third marble and so on until the last marble started rolling away.
What does the "law of conservation of energy" state?
Energy cannot be created nor destroyed, only change forms!
What does the "law of conservation of momentum" state?
Changes of momentum in an isolated system must be equal. (The momentum has to be the same before I hit the baseball as after I hit it.)
In what circumstances would street maintenance people want to increase the friction on the roads? How would they do this?
If it is snowy/icy! They do this by adding salt to the roads to melt the snow/ice.
I'm pushing with all my strength on a wall trying to knock it over, but it won't budge. How much work am I doing? Why?
None! The wall is not moving therefore there is no change in position and no work done.
When we made catapults, where was the potential energy of the system coming from? What was being stretched outside of its natural resting position?
The rubber band at the very bottom of the catapult! When you pulled the arm down, the rubber band was stretched and wanted to shrink back to where it was giving your catapult potential energy.
What is the definition of "force"?
A push or pull!
What is the definition of "tension"?
A continuous pull on an object!
What are the two things that make up momentum?
Mass and velocity!
Remember, momentum is a made up of an object's mass and velocity. If I can't change how much a ping-pong ball weights, how could I give it enough momentum to knock over a heavy domino?
Increase it's velocity by throwing it harder!
If I do it just right, what happens if I shoot a penny at a penny that's not moving? Why?
The first penny that was moving transfers its momentum to the stationary penny. The stationary penny starts moving and the penny that was moving stops.
What is the definition of "work"?
A change in position due to an applied force!
What is "friction"?
A resistance to movement!
Describe the transfer of energy between kinetic energy and potential energy that occurs during a roller coaster ride.
A chain pulls the roller coaster up the hill. As the cart gets higher and higher, it gains more and more potential energy. At the top of the hill, it has the maximum amount of potential energy it will have. As the cart starts moving down the hill, that potential energy is converted to kinetic energy and it builds up speed. As the cart moves up the next hill, that kinetic energy is transferred back into potential energy and the cycle repeats itself.
What happens to mechanical energy that causes a moving object to slow down and eventually stop?
It gets transferred into another form of energy like heat or sound.
Kinetic energy is moving energy, or energy that is being used. In our catapults, how was this kinetic energy expressed?
In the swing of the arm and the pom-pom flying off.