Presentation on theme: "Do Now: A 2.5-kg rock loses 375 J of potential energy while falling to the ground. What is the rock's speed just before it strikes the ground?"— Presentation transcript:
Do Now: A 2.5-kg rock loses 375 J of potential energy while falling to the ground. What is the rock's speed just before it strikes the ground?
Simple Machines 2/9/11
Machine: A machine eases the load by changing either the magnitude or the direction of a force to match the force to the capability of the machine of the person
Lever A lever is a stiff bar that rests on a support called a fulcrum which lifts or moves loads.
Pulley A pulley is a simple machine that uses grooved wheels and a rope to raise, lower or move a load
Wheel and Axle A wheel with a rod, called an axle, through its center lifts or moves loads.
Inclined Plane An inclined plane is a slanting surface connecting a lower level to a higher level.
Wedge A wedge is an object with at least one slanting side ending in a sharp edge, which cuts material apart.
Screw A screw is an inclined plane wrapped around a pole which holds things together or lifts materials.
Do Now (2/8/12): Identify at least two examples of each of the following simple machines: 1. Lever 2. Pulley 3. Wheel and axle
Machines Machines make work easier by decreasing the force required The work stays the SAME; the distance increases W = F d d
Mechanical Advantage The ratio of the resistance force to the effort force Force of resistance: weight of load Effort force: force exerted
Ideal Machines Transfer all energy; work input = work output
Ideal Mechanical Advantage
Examples Please take out your Simple Machines worksheet
Practice Please use the rest of class to work on the paper “Machines.” It is due on Friday! *note – unit test on Energy, Work and Power will be on Tuesday, February 14 th.
Efficiency 3 formulas
Do Now (2/9/12): A worker is testing a pulley system to find the heaviest object that he could lift. The largest force that he could exert is 380 N. When the worker moves the rope 3 m, the object moves.65 m. 1. What is the heaviest object he could lift? 2. What is the mechanical advantage? 3. What is the IMA? 4. What is the efficiency?
Agenda: 1. 3 rd quarter project 2. Finish up homework 3. Begin working on notecards for test
Do Now (2/10/12): A worker is testing a pulley system. The largest force that he could exert is 320 N. When the worker moves the rope 4 m, the object moves.75 m. The weight lifted is 540 N. 1. What is the mechanical advantage? 2. What is the IMA? 3. What is the efficiency?
Pass in: homework Do Now’s
Work Work at an angle
Do Now (punks!): A physics book of unknown mass is dropped from a height of 6 m. what is the speed of the book before it hits the ground?
Do Now: 1. If a 2kg object drops 50 m, how much potential energy did it lose? 2. What is its kinetic energy at the bottom?