p MA= OF/IF 3. A) MA= OF/IF B) MA= OF/IF

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Presentation transcript:

p. 287 2. MA= OF/IF 3. A) MA= OF/IF B) MA= OF/IF MA= 15000N / 350 N = 42.9 3. A) MA= OF/IF MA= 10N / 5.2 N = 1.8 SR= ID/OD 1.0 M / 0.5 M = 2.0 B) MA= OF/IF MA= 20.0 N / 7.0 N =2.9 SR= 30.0 M / 10.0 M= 3.0

P. 287 3C) MA= OF / IF 4. Efficiency = (MA / SR) x 100% MA= 4.0N / 10.0 N =0.4 SR= ID/OD SR= 0.4M / 0.8M= 0.5 4. Efficiency = (MA / SR) x 100% A) 90% B) 97% C) 96% 5. Friction opposes the motion of an object and increases the force required for movement. It also creates waste heat in a system.

The science of work 2.2

copy this down Work Work – done when a force acts on an object to make the object move. - Movement is needed before one can say that work has been done. - Amount of work done depends on 2 things: 1) amount of force exerted on the object 2) distance the object moved in the direction of the applied force.

Work Work (N*m) = Force (N) * Distance (m) N*m is called a Joule (J) copy this down Work Work (N*m) = Force (N) * Distance (m) N*m is called a Joule (J) The joule is also used in calculating energy

Work Questions

Work Answers 250 NM or 250 J 500 N 80 000 NM or 80 000 J 500 J 10 N

copy this down Energy and Work Energy and work are closely related, can not have one without the other. Ex) Car – needs energy (gasoline) in order to work (move) Machines help us do work by transferring energy.

copy this down Work and Machines Using a machine does not decrease the amount of work, it decreases the force. Ex) Work Input = Work Output - This equation is affected by friction (just like mechanical advantage) - Here is another way of calculating efficiency. Work Output Efficiency = ________________ Work Input

Work Efficiency

Work Efficiency Answers 80% 60% 67% 50% 60 85.7 80 J

Formulas to Know MA= Output force/Input force S=Distance/Time (m/s) SR= Input distance/ output distance Efficiency= (Output/ Input)X 100% OR MA/SR W= F x D (Nm)

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copy this down Practice Questions P. 292 1, 2, 6, 7, 8, 9