The Mysteries of Life s1

Name: ______Period: ______Folder______

The Mysteries of Life Dear Tim and Moby,

We’re learning about levers in ~with Tim and Moby: levers science, and I’m totally confused. Can you explain them?

Carlo (Florence)

I think Moby just got a taste of levers in action. Levers are pretty simply, really. They allow us to move things more easily by magnifying our efforts.

A lever has four components: The lever itself is a length of relatively stiff material. The fulcrum is the point on which the lever balances, or pivots. The load is the weight or resistance that needs to be overcome, and The Effort is the force that you apply to the lever.

These elements can be rearranged to make three kinds of levers.

This is a class one, or first class lever. The fulcrum is positioned between the effort and the load. A seesaw is a good example of a class one lever. So is an old-fashioned scale.

The thing to remember with levers is that the distance and effort are interrelated (Note From Mrs. Stevens - That means they are related to each other and changing one changes the other) If you’re willing to increase the distance over which you exert force, then you can decrease that force and still get the job done. Name: ______Period: ______Folder______It’s like the difference between lifting a safe straight up over your head and pushing it up a hill to the same height. The total amount of effort expended is the same in both cases, but pushing it up the hill lets you extend the effort over a longer distance, so you don’t have to push as hard.

Lets take a look at this simple class one lever. See how the fulcrum is in the middle? Lifting Moby in this case requires a lot of force. --Beep. --You don’t have bones.

Anyway, this is the distance over which we have to exert force to lift Moby to the top. We can increase this distance by moving the fulcrum towards him. Since the distance is increased, the amount of force needed to lift him is decreased.

Lets see some more levers. The fulcrum in a class two lever can be found at one end, with the effort applied at the other end. The load is somewhere in between. A wheelbarrow is a class two lever. Since the load is close to the fulcrum, the effort needed to lift the load is spread out and lifting is easier.

In both class one and class two levers, the effort needed to move the load is smaller than the load, but the effort travels further. Name: ______Period: ______Folder______Class three levers have the fulcrum at one end, like a class two lever. But in a class three lever the position of the effort and load are reversed.

Here, the effort needed to move the load is actually greater than the load itself, but the load moves further than the effort.

Tweezers are class three levers. So is your arm!

Before Moby and I understood levers, playing on a seesaw was about as much fun as waiting for a bus. Nrgh!

But if Moby, who weighs about twice as much as me, moves halfway up the seesaw, we can balance with no problem.

Waaaah! Name: ______Period: ______Folder______

Example of a Class One Lever:

Example of a Class Two Lever:

Example of a Class Three Lever: Name: ______Period: ______Folder______

There are two methods for calculating the mechanicalThe advantage ofLever a lever; *Both are ratios *Both compare one side of the lever to the other

Method 1: MA = Length of the Effort side of the lever ÷ Length of Resistance side of the lever

Method 2: MA = Effort force (Newtons) ÷ Resistance force (Newtons)

Reminder: When calculating MA, the input and output numbers will be in units of distance (feet, meters, etc). However, the final answer has NO unit – it is a ratio, just a number that tells us the answer to the question “how much easier does the tool make the job”

Effort Length ÷ Resistance Length = MA (“person side”) (“object side”) Method 1 Practice: Ratios of Length (distance) 1 15 inches ÷ 3 inches = 2 12 feet ÷ 4 feet = Reminders: 3 ÷ 15 in = 3 Solving for C.1 (C.2 x C.3) Solving for C.2 (C.1 ÷ C.3) 4 ÷ 3 ft = 6.5 ______5 70 feet ÷ = 10

Method 2 Practice: Load Force ÷ Effort Force = MA Ratios of Force (“object weight”) (“person’s effort”) 6 100N ÷ 25N = Reminders: Solving for C.1 (C.2 x C.3) 7 600N ÷ = 5 Solving for C.2 (C.1 ÷ C.3) 8 4,500N ÷ = 8 9 20N ÷ 10N = 10 ÷ 75N = 3 Name: ______Period: ______Folder______

Word Problems Part 1: Ratios of Length Effort length ÷ Resistance = MA (person side) length (object side) 11 A construction worker uses a board and log as a lever ÷ = to lift a heavy rock. If the effort arm is 6 meters long and the resistance arm is 0.75 meters long, what is the MA?

12 A lever used to lift a heavy box has an effort arm of 4 ÷ = meters and a resistance arm of 0.8 meters. What is the MA?

13 A lever with a resistance arm of 2 centimeters has a ÷ = mechanical advantage of 4. What is the output arm’s length?

14 A rake is held so that its effort arm is 6.4 meters and its ÷ = resistance arm is 1.25 meters. What is the mechanical advantage of the rake?

15 Acrobats at the circus are using a lever to propel each ÷ = other into the air. When the lever is measured, it shows the effort arm is 8 meters long, the resistance arm is 2 meters long. What is the MA? ÷ ÷ Word Problems Part 2: Ratios of Force Load Force Effort Force = MA Fill out the formulas, and calculate the missing (object (person’s information weight) effort)

16 If the mechanical advantage of a lever is 5, and the ÷ = load force is 500N, what is the effort force?

17 By using a lever Jonathon can lift a load of 3000N ÷ = using an effort of just 300N, what is the mechanical advantage of the lever?

18 Stephen pushes down with a force of 60N to just a load ÷ = of 300n off the ground. What is the mechanical advantage of the lever?

19 If the mechanical advantage of a lever is 3, and it took ÷ = 240N of effort force to lift the load, how many newtons of resistance did the load provide?

20 By using a lever Marissa can lift the load using an effort ÷ = of just 300N, if the mechanical advantage of the lever is 4.5, what was the resistance force of the load in newtons? Name: ______Period: ______Folder______