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Name:________________________________________ Simple Machines Study Guide
Force and Work-
1.) To be considered work, you have to have a ______force ___ and a ___ distance ____ through which the force acts.
2.) What is the formula for work?__ work = force x distance _ What is the unit for work?__ joules_
3.) What does something have to do to be considered a machine? A machine is any device that makes doing work easier.
4.) Decide if work is done for each of the following: (Are the requirements for WORK met?) a. Someone is sitting on a cushion on the floor. Work or NO work b. A baseball is hit into the bleachers. Work or NO work
c. Ms. Jarrett holds a doorstop in one place to show you an example of a wedge. Work or NO work d. A little girl is pushed on a swing. Work or NO work
Simple Machines Basics
1.) What are the 2 basic types of simple of machines, of which all other simple machines are variations of? Also list the other simple machines in the correct category under the heading.
___inclined planes_____ & ________levers_____
Wedge pulley
Screw wheel and axle
2.) In general, what do most simple machines do?
Simple machines make work easier by reducing the force needed.
3.) Do simple machines make less work? Explain.
No. Simple machines make work easier, they do not decrease the amount of
work. Simple machines can actually make more work due to friction.
4.) What do we mean when we say “machines make work easier ?” (force vs. distance) Simple machines make work easier to do by decreasing the force required by increasing the distance over which the work is done.
5.) A force applied by a machine to an object is the? a.) resistance force b.) effort force c.) force field d.) Jedi force
6.) A force applied to a machine by a person is the? a.) resistance force b.) effort force c.) force field d.) Jedi force
7.) Simple machines make work easier, however there are 2 exceptions to this rule. What are the exceptions, and in each case, what is the “advantage” each machine gives us?
- single fixed pulley – changes the direction of a force
- 3 rd^ class lever – gives us increased speed
Inclined Plane
1.) An inclined plane decreases the ___ force ____ needed to lift an object by
_____ increasing ___ the distance that force is applied.
2.) In general, less force = __ more __ distance, and more force = __ less ____ distance
3.) If the force required to lift a barrel into the back of a truck was 124 Newtons without a simple machine, what would the force required to get the barrel into the back of the truck using a ramp? (Think in general, you don’t have enough info to calculate.)
a.) less than 124 Newtons b.) more than 124 Newtons c.) 124 Newtons
4.) Inclined planes can increase the amount of work done due to ________ friction ____.
5.) If it takes 45343 joules of work to lift a barrel into the back of a truck without using a simple machine, how much work would be required to get the barrel into the back of the truck using a ramp? (Think in general again, and CONSIDER FRICTION)
a.) less than 45343 Joules b.) more than 45343 Joules c.) 45343 Joules
If we consider friction, we can conclude that the work would be slightly more due to the friction.
Lever
1.) A lever turns on a fixed point, called the __ fulcrum _____. 2.) Other than multiplying a force, what else can levers do? Change the direction of a force
3.) Explain how you would determine what class a lever is. (Look where and be what?) Look in the middle and be FRE --- fulcrum in middle = class one, resistance in middle=2, effort in the middle = class 3
4.) What happens to the force needed to move an object as you increase the length of effort arm? force needed would DECREASE as you increase the effort arm
5.) What would happen to the force required if you decreased the length of the effort arm? If you decreased the effort arm, the force needed would increase
6.) True or False and explain- ALL LEVERS make work easier.
FALSE. The third class lever does
NOT make work easier. They give
you increased speed.
7.) Label the effort, resistance and fulcrum in the pictures below an identify what class of lever it is.
4.) Would machines with higher mechanical advantage would take more or less work to make something move? A.) more (with friction) b.) Less c.) the same
5.) If you have a choice between a machine with a MA of 4 and a machine with an MA of 6, which machine would it make more sense to use?
MA of 6 – you would not have to use as much effort force
Wheel and Axle-
1.) Object with larger radius= __ wheel , object with smaller radius= axle _____________
2.) What would be easier (take less force ) to turn and why: An axle with a diameter of 10cm using a 100cm wheel An axle with a diameter of 10cm using a 50cm wheel Why?- I t has a larger effort wheel (large wheel). When you increase the effort distance, you decrease the effort force needed.
3.) What would require the least amount of work to turn and why : An axle with a diameter of 10cm using a 100cm wheel An axle with a diameter of 10cm using a 50cm wheel Why?- Both amounts of work are the same due to the axles being the same. The 100cm wheel would just be easier because it travels a greater distance.
4.) Calculate the IMA for the following machines. Show your work.
Rw = 11 cm Ra = 0.5 m dw = 2.4 m Ra = 3 cm Rw = 3 m da = 0.8 m IMA=3.7 IMA = 6 IMA = 3
The Screw-
1.) Which of the screws to the right (A or B) would require the greatest amount of force to drive into a piece of wood? Why? A – There are less threads so there is less distance. There is more force required for a screw with less distance.
2.) Which of the screws to the right (A or B) would be the easiest to drive into a piece of wood? Why? B – There are more threads so there is more distance. Since the rule is the greater the distance, the less the force, there is LESS force required for the screw with more threads.
3.) Which of the above screws (A or B) would have the greatest mechanical advantage? B – more threads, more distance, less force
4.) What is a specific advantage we discussed of using a screw instead of an inclined plane? (Think staircases) completing the same goal using a smaller space
The Wedge
1.) What does the wedge do as it moves into a material? Separates the material
2.) Of the two wedges to the right, which do you think would require the least amount of force if you wanted to separate those objects 8cm and why? B- it has a greater distance (length) and the rule is when you increase the distance, you decrease the force (make work easier)
4.) What is a major difference between the wedge and an inclined plane? The wedge moves
3.) Measure and calculate the IMA of the wedges.
Calculations: Show your work! Work = force x distance
You will be given the following on your test: Length of slope IMA wedge = --------------------------
FR DE Height or thickness
Radius wheel
MA x FE IMA x DR IMA wheel and axle = -------------------------
Radius axle MA = Resistance Force I.M.A = Effort Distance Effort Force Resistance Distance
1.) A clown is trying to lift a refrigerator full of wigs a height of 2M. It would take him a force of 60 Newtons to lift the fridge without a simple machine.
a.) Exactly How much work would be required to lift this fridge of wigs without a machine?
Force= 60 N Distance= 2 M
Work = Force x Distance W= 60 Newtons x 2 M Work= 120 Joules
b.) Assuming no friction, how much work would be required to lift the fridge of wigs with a lever that has a mechanical advantage of 6?
120 joules – the amount of work would not change by using the machine, the work would just be easier
c.) Assuming no friction, how much effort force would be required to lift the fridge of wigs with a lever that has a mechanical advantage of 6? 60 N / 6 Force = 10 N
Height = 2.6 cm
Slope = 2.4 cm
IMA = 2.4cm/2.6 cm =.
Height = 1.8 cm
Slope = 3 cm
IMA = 3 cm/1.8 cm = 1.
