1. Physics Review Project Nathan Hayes, Austin Alpern, Evan Alpern, Chance Roedel

2. Forces and Newton’s Laws ●A force is a push or a pull applied by one object and experienced by another object. ●The net force on an object is the single force that could replace all the individual forces acting on an object and produce the same effect. o Forces acting in the same direction add together to determine net force o Forces acting in opposite directions subtract to determine net force ●Weight is the force of a planet on an object near that planet. ●The force of friction is the force of a surface on an object. The friction force acts parallel to the surface o Kinetic friction is the friction force when something is moving along the surface and acts opposite the direction of motion o Static friction is the friction force between two surfaces that aren’t moving

3. Forces and Newton’s Laws ●The normal force is the force of a surface on an object. The normal force acts perpendicular to the surface. ●The coefficient of friction is a number that tells how sticky two surfaces are. ●Newton’s First Law says that an object in motion will stay in motion and an object at rest will stay at rest unless acted upon by an outside force. ●Newton’s Second Law states that an object’s acceleration is the net force it experiences divided by its mass and is in the direction of the net force. ●Newton’s Third Law states that the force of Object A and Object B is equal in amount and opposite in direction to the force of Object B on Object A.

4. Important Formulas ●F net = ma o The net force is equal to the object’s mass (in kilograms) multiplied by its acceleration in that direction. ●F f = uF n o The friction force is equal to the coefficient of friction times the normal force.

5. Example Problem ●A box weighing 5400 N is being pulled up a frictionless inclined plane that rises 1.3m for every 7.5m of length measured along the incline. Determine the magnitude of the force applied parallel to the incline necessary to move the box up the incline at a constant speed.

6. Step 1: Draw a diagram of the situation Step 2: Draw a free body diagram for the situation 7.5 m 1.3 m F g (Gravitational Force) F p (Force parallel to motion) F n (Normal Force)

7. Step 3: Rotate the free body diagram Step 4: Use the triangle to calculate the angle of ascent 5400 N 7.5 m 1.3 m O tan O = 1.3 7.5 O = tan -1 (1.3/7.5) O = 10 o

8. Step 5: Use SOH-CAH-TOA to solve for F p 5400 N 10 o Fg y Fg x F gx = 5400 N x sin(10) = 938 N Since “everything up equals everything down and everything right is equal to everything left,” the force that is parallel to the motion is equal to the horizontal component of gravity F p = 938 N

9. Work and Energy ● Within a system, energy can be transformed between various forms. ● Energy can be transferred into or out of a system in two basic ways: ● Work: The transfer of energy by mechanical forces. ● Heat: The nonmechanical transfer of energy from a hotter to a colder object.

10. Conservation of Energy ● When work W is done on a system, the system’s total energy changes by the amount of work done. In mathematical form, this is the work-energy equation: ∆E=∆K+∆Ug +∆Us +∆Eth +∆Echem +... =W ● A system is isolated when no energy is transferred into or out of the system. ● This means the work is zero, giving the law of conservation of energy: ∆K+∆Ug +∆Us +∆Eth +∆Echem +... =0

11. Important Concepts ● Kinetic Energy is the energy of motion. o ½mv^2 + ½Iw^2 o Since the first part of the equation is translational and the second part is rotational, the second part is often omitted. ● Potential Energy is energy stored in a system of interacting objects o Gravitational potential energy: Ug = mgy o Elastic potential energy: Us = ½kx^2 ● Mechanical Energy is the sum of kinetic and potential energies o K + Ug + Us

12. Important Concepts ● Thermal Energy is the sum of the microscopic kinetic and potential energies of all the molecules in an object. o The hotter an object, the more thermal energy it has. o When kinetic friction is present the increase in thermal energy is ∆Eth =fk∆x ● Work is the process by which energy is transferred to or from a system by the application of mechanical forces. o If a particle moves through a displacement d while acted upon by force F, the force does work: W=FdcosØ

13. Applications ● Perfectly elastic collisions are where both mechanical energy and momentum are conserved.

14. Application ● Power is the rate at which energy is transformed

15. Example Problem

16. Example Solution

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