PHYSICS – 8.4 NOTESSimple Machines

I. The simple machine

A. Types of Simple Machines…1. Lever2. Pulley3. Wheel and axle4. Screw5. Wedge6. Inclined plane

B. Def –C. Table 8-6 pg. 298D. Using Simple Machines

1. Mechanical Advantage – ratio of forceout compared to forcein

a. 2. MA – ratio of distancein

compared to distanceout

a.

Any device that transmits or modifies force

3. Ex: A carpenter uses a claw hammer to pull a nail from a board. The nail has a resistance of 2500 N. The carpenter applies a force of 125 N. What is the mechanical advantage of the hammer?

4. Ex: A 3.75 meter long ramp is used to get a 1000 N sofa onto the back of a 1.25 meter high trailer. What is the ideal mechanical advantage of the ramp?

3 .oo MA

20.0 MA

E. What machines can do…1. alter force and distance

MA > 1 force in reduces, but… distance increasesMA < 1 force in increases, but… distance decreases

F. Efficiency (real machines)1. Def –

2. a. 100% efficient???

3. Ex: A sofa weighing 1000 N must be placed in a truck bed 1.2 m off of the ground. A worker uses a force of 500 N to push the sofa up the inclined plane that has a slope of 3.5 m. What is the efficiency of the inclined plane?

How much input energy is lost compared to how much energy is used to perform work on an object.

70% Efficient

Physics Assignment

1. The efficiency of a squeaky pulley system is 73%. The pulleys are used to raise a mass to a certain height. What force is exerted on the machine of a rope is pulled 18.0 m in order to raise a 58 kg mass a height of 3.0 m?

2. A person lifts a 950 N box by pushing it up an incline. If the person exerts a force of 350 N along the incline, what is the MA of the incline?