Name: Simple Machines Study Guide Force and Work-

1 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.

2 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 .

3 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?

4 1. single fixed pulley changes the direction of a Force 2. 3rd 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.

5 124 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.

6 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 7.) Label the effort, resistance and fulcrum in the pictures below an identify what class of lever it is. Pulley 1.) Pulleys can ___multiply____ a Force or change is _____direction____. 2.) What are the three types of pulleys? Single movable, single fixed, block and tackle 3.) How do you find the mechanical advantage of a block and tackle? Count the sections of rope supporting the weight 4.) True or False and explain-ALL PULLEYS make work easier. FALSE. Fixed pulleys do not make work easier, they only change the direction of the Force . 5.) How does the distance of the string you pull compare to the distance the weight is lifted when using a block and tackle system?

8 The distance of the string you pull is much greater than the distance the object is lifted. (Trading increased distance for decreased Force .) 6.) What is the MA of a single fixed pulley? ___1_____ single movable pulley? _____2_____ 7.) Find the effort Force required to lift the 300 N weight in the diagram. 1- 300 N 2- 100 N Simple vs. Compound Machines (mentioned in Machines reading) 1.) What makes something a compound machine instead of a Simple machine? Composed of 2 or more Simple Machines 2.) Label each machine with S for Simple and C for compound. a. scissors __C__ d. pry bar __S____ b. ramp __S_____ e. bicycle __C____ c.

9 Single fixed pulley ____S___ f. shovel ___S____ 3.) List 3 of your own examples of compound Machines . (Remember: Machines help make work easier. Bull dozer, wheelbarrow, nail clippers, etc Mechanical Advantage Basics 1.) Mechanical advantage is how much the machine ___multiplies__ your Force . 2.) What does it mean about a machine if it has a mechanical advantage of 1? The Machines doesn t increased your effort/ input Force . The Force the machine applies to an object is the same as the Force you put in. It doesn t help you by making you stronger. 3.) Would Machines with higher mechanical advantage would take more or less effort Force to make something move?

10 A.) more b.) Less c.) the same 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?