Levers and Pulleys

Investigation 1 Levers

Can you lift me off the floor with one hand?

Title : Introduction to Levers Purpose: To understand what levers are and their purpose Q?

So What are Levers? Levers are tools that people use to make work easier. Levers are used to lift things to overcome resistance. Levers give us an advantage by making work easier Today, we are going to find out how levers can make work easier.

Building our Lever systems A lever arm is a stick or beam, free to pivot at a point. We will be using the ruler as our lever arm The fulcrum is the point which the lever arm pivots. We will be using the binder clip as our fulcrum The mass lifted by the lever is the load. Is the black square weight The effort is the force (push or pull) needed to lift or move the load We will be providing the effort in our systems

Let’s Build Levers Getters, please get your baskets with the following supplies: 2 Half-meter sticks 2 Binder clips 2 Dowels 2 Loads 2 Erasers Duct tape Already have groups made.

OBservation: In your notebook record… Can you lift the load using only one finger? Does it always take the same amount of force to lift the load? Where should you press to lift the load with the least force?

Introduction to Levers Line of Learning (LOL) A lever is a simple machine that is used to gain mechanical advantage, such as making work easier. A lever arm is a stick or beam that is free to pivot at a point A fulcrum is the point where the lever arm moves. The load is the weight. The effort is the force used to move the load. Lever Arm

Title: Intro to levers part 2 (Reading a Spring Scale) Purpose: To learn how to measure the advantage of using a lever. Q? How can you measure the advantage provided by a lever?

Effort is a force, and force is measured in newtons (N). Newton is the unit used to measure force in the metric system. Gram is the unit used to measure mass or Liter is used to measure volume.

Reading a Spring Scale Scale readings are made at the top of the little metal indicator. Each little line on the Newton scale represents 0.2 N. When the indicator rests between the two lines, estimate to the closest 0.1 N.

Norms for Using a Spring Scale Always zero the scales before starting the task. Always use the scale right side up, never upside down. Pull until the lever arm is level, then read the effort. (One person should pull the scale while another reads the scale) Stop before the scale goes past the 10-N limit.

Levers: Reading a Spring Scale Get your table baskets Build your lever systems Practice using your spring scale Record observation Reminders… Scale readings are made at the top of the little metal indicator. Each little line on the Newton scale represents 0.2 N. When the indicator rests between two lines, you should be able to estimate to the closest 0.1 N.

Introduction to levers Cont. Line of Learning (LOL) Vocabulary: Newton: The unit used to measure effort is a Newton (N). Content: In what ways can a lever provide an advantage? A lever can make a load easier to lift, it can move loads, and it reduces the effort needed. What are the four parts of a lever system? Lever arm Fulcrum Load effort

Title: Lever Experiment A Purpose: To see how moving where the effort is applied effects the effort/force needed. Q? What is the effect of moving where the effort is applied on how much effort is needed to lift the load?

What are the Variables? Independent Variable ( I Change it) – Dependent Variable ( Wait and SEE) Constants (Stays the same) The position of the effort. How much work or force is needed. the load, the lever arm, fulcrum

Procedure Demonstration I built my lever system Now, I will place my load at 5cm from the fulcrum on my lever arm, and the scale at 25 cm from the fulcrum on the other side. The load is at 5cm from the fulcrum. How much pull am I applying to lift the load? What does my spring scale say?

How can we figure out how much the scale weighs? Make sure students understand that scale pulls with it’s own force of .5 N, so we always have to add . 5 N when pulling down.

Procedure Begin Lever Experiment A. Record the effort needed to lift the loadin the left half of the “effort” column. Add the effort of the scale in the right hand side. Use the chart to know where to apply the effort We will graph our finding together.

Observations Any benefit you can get from using a lever is called advantage. Did the lever give you any advantage? Did the amount of force needed to lift the load change when you moved the position of the effort? What is the relationship between the position of the effort and the amount of effort needed to lift the load?

Graph the results together

Using our Graph to Make Predictions How much effort would it take to lift a load at 10 cm if the effort were at 22 cm? At 13 cm? At 30 cm? If 4.0 N of effort was required to lift the load at 10 cm, where was the effort applied?

Conclusion What general statement can you make about your graphs? What is the relationship between the load and the effort in a lever system?

LOL Vocab: A two-coordinate graph shows relationships between two variables Advantage is a benefit obtained by using a lever (or other simple machine).

LOL cont Content: 1.When the load is in a constant position on the lever arm, how can you make it easier to lift the load? - The farther the effort is from the fulcrum, the easier it is to lift the load. 2.What is the difference between the weight of the load and the amount of effort needed to lift it? - The weight of the load remains constant (the same); the effort needed to lift the load varies (changes) depending on where the effort is applied on the lever arm.

Real World Example If you wanted to lift a big box where would you apply the effort? A, B, or C? Why B C A

Title: Lever Experiment B Purpose- To see how moving the location of the load effect the amount of effort needed to lift the load. Q? What is the effect of moving the load on how much effort is needed to lift the load?

Procedure 1.Begin Lever Experiment B. Record the effort needed to lift the loading the left half of the “effort” column. 2. Add the effort of the scale in the right hand side. Use the chart to know where to place the load on the lever arm. With your partner graph your findings. Refer back to Lever A experiment if you need help.

Graph and Data Add the image of the graph for Exp B

Graph Observations How does your graph from experiment A compare to your graph from experiment B? What is the relationship between the location of the load on the lever system and the effort it takes to move it?

Using Our Graphs to Infer and make predictions How much effort would it take to lift a load at 10 cm if the effort were applied at: 22cm 13 cm 30 cm If 4.0 N was required to lift the load at 10cm, where was the effort applied?

Conclusion What did you learn? What surprised you? What would you do differently next time?

LOL Content: 1.What is the relationship between the location of the load on the lever system and the effort it takes to move it? -The effort needed to lift the load decreases as the load gets closer to the fulcrum. - The effort increases as the load gets further away from the fulcrum.

Title: Lever Classes Purpose: To identify the different classes of levers Q1? What will happen if the fulcrum is not in the middle; is it still a lever? Q2? Is there any advantage to moving the fulcrum to a new location?

Observations

Conclusion: Did you answer your questions? Did you talk about your findings? Did you talk about what you learned?

Classes of Levers Line of Learning (LOL) Class-1 Lever This lever has the fulcrum in the middle and the effort and load on the outside Example: Seesaw, crowbar, paint can opener

Classes 0f levers Line of Learning (LOL) Class-2 Lever Examples) Wheelbarrow, nutcracker, bottle opener

Classes of Levers Line of Learning (LOL) Class-3 Lever This lever has the effort in the middle and the load and the fulcrum on the ends. Examples) Rake, broom, hammer, human arm, tweezers

LOL Continued Content: How many ways can levers be set up? What is an easy way to remember where the fulcrum goes in each lever? F-1 L-2 E-3

Title: Lever Diagrams Purpose: To learn how to correctly diagram different classes of levers. Q? How do you diagram different classes of levers?

Diagrams

LOL Vocab: A diagram is a drawing that describes the relationship of all the parts of a system. Content: 1. How can we record information about a lever design? -A diagram uses a system of symbols and conventions to communicate information about lever designs?

Title: Real World Levers Purpose: To discover some of the levers in our everyday world and what class of lever they are. Q? What are some levers in our every day World and what type of lever are they?

Real-World Levers What class of lever is the screwdriver used to pry the lid off of a can? Class 1 When you are trying to lift the lid off a can of putty or paint, there is not metal cube to be lifted. Where is the load, and what direction is the load acting?

Real-World Levers Demonstrate the paint can.

Real-World Levers A load can be either a mass that you lift or resistance that you need to overcome. The tight lid on the can requires a lever to get it loose. The resistance is the load. You try to lift the load up, so the resistance (load) is acting down.

Real-World Levers Our Task We are going to observe the tool and decide what class of lever it is. Diagram the lever and label the fulcrum, load and effort. Discuss if the load and effort are pushing down or pulling upward and label it on your diagram.

Real-World Levers What type of levers did we discover. Diagrams (insert picture):

Broom

Nutcracker

Scissors

Bottle Opener

Pliers

Tweezers

Hammer

Human Arm

LOL Where are levers found in everyday use? Many common tools use levers: scissors, pliers, bottle openers, hammers, and brooms. What happens to the effort required to lift a load as the load moves closer and closer to the fulcrum in a class-1 lever, a class-2 lever and a class-3 lever? Effort is reduced as the load moves closer to the fulcrum.

Title: Lever Pictures Purpose: To identify and name different classes of levers. Q? What are the classes of levers of some of the everyday tools we use?

Lever Pictures

Conclusion