Simple Machines Song Pu

Basics of Simple Machines Agenda Student Introduction Rules and Scoring Basics of Simple Machines Homework and exam

Required Device must be impounded Simple Machines Rules Team of 2 Required Device must be impounded 50% of score SI Units Simple Machine Concepts Simple Machine Calculations Simple Machine History Part 1 (Written Test) One known and one unknown mass (50-1200g each) 5:1 (Reg), 7:1 (State), 9:1 (Nat) Part 2 (Device Testing)

Scoring for Both Events Exam Score (ES) is worth 50 points (or 50% of total) Device Measurement counts for 50% of total, with two ratio scores Time Score (TS) = ((240-time)/240*10 points Ratio Score (R1 and R2)=(1-(abs(AM-CV)/AM))*20 points Teams with no device, miss impound, or mass estimate or that do not make an honest attempt = 0 points for Device Measurement Final Score (FS)=ES+TS+RS (maximum of 100 points) Tie Breakers Best ES score Best TS score Specific Test Questions

Simple Machines Simple machines are non- motorized devices that change the direction or magnitude of a force. 6 types of simple machines: Lever (all 3 classes) Inclined Plane Wedge Pulley Wheel and axle Screw

Lever

First Class lever Can be used to magnify the amount of effort exerted and to decrease the speed of effort. Can also be used to magnify the distance and the speed of the effort exerted and decrease its magnitude. The fulcrum is located in the middle.

Second Class lever Can also be used to magnify the amount of the effort exerted The effort and resistance move in the same direction. Effort and resistance are on the same side of the fulcrum but the effort is farther away

Third Class lever Can be used to magnify the distance and the speed of the effort exerted and decrease its magnitude The effort is applied on the same side of the fulcrum as the resistance but the resistance is farther from the fulcrum. The effort and the resistance move in the same direction.

Defining symbols E = effort R = resistance DE= effort distance DR= resistance distance

Formula for Part 1 Effort arm (DE) = Resistance (R ) Resistance arm (DR) Effort (E) E R DR De

Rearrange Formula R = Effort (E) x Effort arm (DE) Resistance arm (DR)

Formula for Mechanical Advantage (AMA) This is an expression of the ratio of the applied force (effort) and the resistance. M.A. = R E First and second class levers provide positive MA because they magnify force. A third class lever actually requires more force than the force of the resistance and this is called fractional MA.

Pulley

Pulleys Pulleys are used to change the direction of the applied force (fixed pulley)

Pulley can also be used to magnify effort (movable)

Wheel and Axle

Wheel and Axle This consists of a wheel or crank rigidly attached to an axle and they move together. The same equation is used for MA but the DE is the radius of the distance through with the effort is applied and DR is the radius of the distance through with the resistance is moved.

Wheel and Axle Example Think about a doorknob. You exert a force on the knob and the small mechanism inside moves. The radius of the doorknob is 3 cm and the radius of the mechanism is 0.3 cm. The ratio of the two gives you an MA of 10. Much easier to turn!

Inclined Plane

Inclined Plane Inclined Plane permit you to overcome large resistances by applying a relatively smaller force through a longer distance.

Inclined Plane If this block has a mass of 60 kg and you need to move it up a 30 m ramp to a 10 m level what is the IMA? 30 m 10 m

Wedge

Wedge A wedge is simply two inclined planes side by side. It is used to divide two areas with great efficiency.