Presentation on theme: "Question O’ The Day What is a force?"— Presentation transcript:
1Question O’ The Day What is a force? Take 1 minute and 37 seconds and talk about it with the people sitting around you. Be AS SPECIFIC as possible. (Bonus points for using the words vector or scalar in your explanation).
2Writing Assignment O’ The Day On your whiteboardWrite down absolutely anything you know (or think you know) about forces.It doesn’t matter if you’re right or wrong I just want to know what you think.
3Force is…A force is a push or a pull resulting from an interaction between objects.Since you can’t push or pull without doing so in a direction…force is a vector.The unit for force is….ehh actually we’ll wait a couple of days for that one.
4Gravitational Force The force between two objects that have mass. ALL objects that have mass are gravitationally attracted to each other.
17Free Body DiagramsFree body diagrams are used to represent the forces acting on any given object.Let’s do some (actually…a whole bunch of) practice problems.Come on up and grab whiteboards.On one whiteboard sketch out the system schema.On another whiteboard sketch out the Free Body Diagram
18Free Body DiagramsA book is at rest on a tabletop. Diagram the forces acting on the book.
19Free Body DiagramsA person is suspended motionless from the ceiling by two ropes. Diagram the forces acting on the person.
20Free Body DiagramsAn egg is free-falling from a nest in a tree. Neglect air resistance. Diagram the forces acting on the egg as it is falling.
21Free Body DiagramsA flying squirrel is falling vertically from a tree to the ground at constant velocity. Consider air resistance. Diagram the forces acting on the squirrel.
22Free Body DiagramsA rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.
23Free Body DiagramsA rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.
24Free Body DiagramsA college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder. Diagram the vertical forces acting on the backpack.
25Free Body DiagramsA skydiver is descending with a constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver.
26Free Body DiagramsA force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration. Diagram the forces acting upon the sled.
27Free Body DiagramsA football is moving upwards towards its peak after having been booted by the punter. Diagram the forces acting upon the football as it rises upward towards its peak. Neglect air resistance.
28Free Body DiagramsA car is coasting to the right and slowing down. Diagram the forces acting upon the car. Neglect air resistance.
29Elevator Activity: 1.24.14 Elevator Activity Big Ideas:Unbalanced forces cause acceleration (speed up or slow down).Balanced forces mean things are moving with a steady velocity.
34Law of Laziness Mr. Heffernan’s Law of Laziness- If something is not moving it will keep not moving unless something makes it move.If something is moving it will keep moving in the same way unless something makes it change how its moving.
35Newton’s First Law Newton’s 1st Law- An object moves with a constant velocity unless a force causes it to accelerate.
36InertiaInertia- The resistance of an object to a change in it’s motion.Inertia = LazinessThe inertia of an object is directly proportional to its mass.Mo’ Mass, Mo’ Inertia
55Static Friction Our lab took a look at static friction Ffs. As applied force was increased…static frictional force increased to a maximum value.
56Kinetic FrictionIn order to take a look at kinetic friction…let’s do a gedanken experiment(Say experiment).It is generally harder to get a heavy object moving than it is to keep it moving.Because of this… μs is generally greater than μk.
66Da Spring Konstant How far the spring stretches or compresses Spring ConstantSpring Force
67Da Spring KonstantThe spring constant is a measure of how difficult it is to stretch or compress a spring.As the spring constant goes up…spring forces goes ______ for the same displacement?As displacement goes up….the spring force goes _______ for the same spring?The spring constant ONLY depends on what kind of spring you have.
69Balanced Forces Practice Springs and 1D Balanced Forces Practice
70Back in high school, my buddy used to drive this truck. Naturally, his truck broke down and we had to push it back to his house.One of my friends decided to try and pull the truck instead of push it.Since that truck is long gone, lets model this with pulling a 2kg mass.
71The following box is sitting on a table located on Earth The following box is sitting on a table located on Earth. The box is not moving. Determine the value of the missing forces.5N30°2kg