Physical Science Lab the Lever Other Simple Machines #1

General Physics: The Lever  STEP ONE: Getting to Know You Begin your study of the lever by clicking on the above link (or click HERE ), and then click on the first box, titled “Intro.” Play with the simulator for a few minutes until you feel comfortable with its controls and how it operates, and then proceed to Step Two. (Note: In Step Two, you will need to unscramble some basic terms. Write these on the lines provided.) STEP TWO: Background Information A lever is a simple machine that multiplies either force, OTMION ______________, or both. A typical lever consists of a rigid bar that rotates around a fixed point that VOPSIT_____________. This is known as the fulcrum. The lever is one of six basic simple machines. The other five are the HEWEL ___________ and axle, the PLEULY ____________, the inclined plane, the GEDWE ____________, and the CREWS __________. Technically speaking, these last two simple machines are actually different versions of the LINNCIED _____________plane because of their matching physical characteristics. Complex machines like this excavator typically use all six of the simple machines in a variety of unique and important ways. The excavator’s two main levers, the boom and the arm, are used as force TIPLMULIERS __________________, as they allow for the movement of material far in excess of what is possible by hand. Notice how the fulcrum (A) is just one of many VOPSIT_____________ points that allow the excavator to move of enormous masses of material. There are four aspects of a standard lever. The force, or FOREFT ___________ is what is applied to the EVREL _______. The purpose of this force is to move or redirect the load, also known as RTANESISCE ________________. In the case of the excavator, you can see four hydraulic pistons that apply this force to the boom and the arm. (To see excavators in action, click HERE.) There are three general types of levers—Class I, Class II, and Class III. With each type of lever, the goal remains the same: multiply force and/or motion. Shown to the right is the 1st Class Lever. It is perhaps the most popularly known lever. With this lever design, the fulcrum sits between the load and the force. The force or effort applied to the lever is in the opposite direction of the load. Increasing the efficiency of the lever can be done in one of two ways. Decreasing the distance from the load to the fulcrum is one way of moving the load while using less force (energy). Increasing the distance between the force (or effort) and the fulcrum is the second way in which the load can be moved using less energy. The 2nd Class Lever, shown to the left, has the fulcrum at one end of the lever. Oftentimes, a wheel is found at the fulcrum of a 2nd class lever, which makes for transporting loads much easier. Increasing the efficiency of the 2nd class lever can be done in the same manner as was shown with the 1st class lever. The load can be moved using less energy either by decreasing the distance between the load and the fulcrum, or by increasing the distance between the force and the fulcrum. The 3rd Class Lever has the fulcrum situated at the end of the lever, much like what is seen with the 2nd class lever. However, in this lever design, the force and the load have changed places on the lever. As with the previous two levers, the load can be moved more easily (with less energy / force expended) by either moving the load closer to the fulcrum or by moving the force farther away from it. Before moving on to the actual mathematics of calculating the forces involved with a lever, let’s do a quick check-up to see if you have an adequate understanding of what has been presented so far. Comprehension Check-Up 1.) LABEL the following three types of levers as Class I, II, or III. LEVER TYPE:______ LEVER TYPE:______ LEVER TYPE:______ 2.) What are the six types of simple machines? LIST these below. 3.) “All levers involve a fixed point that …. This point is known as the fulcrum.” a. slides b. turns c. pivots d. bends 4.) LABEL these common applications of the 3 levers. Each lever type is used twice. 5.) Say you wanted to increase the efficiency of your 1st class lever. You want to do more work using less force or energy. How could you do this? (Choose 2 answers below.) a. Increase the distance between the load and the fulcrum. b. Decrease the distance between the load and the force. c. Decrease the distance between the load and the fulcrum. d. Increase the distance between the force and the load. 6.) With a typical excavator, which part is largest lever on the machine? a. The bucket b. The boom c. The arm d. The counterweight 7.) Place a circle around this largest lever. STEP THREE: The Lever Formula The relationship between force and distance is expressed as a mathematical formula. This formula is known as the Law of the Lever . It is expressed as: F1 x D1 = F2 x D2. That is, the force (or mass) on one side of the lever multiplied by the distance of this force or mass to the fulcrum is equal to the second force or mass times its distance to the fulcrum. If these products are equal, the masses will balance. Or, put in another way, the masses (or forces) are in equilibrium. Now let’s look 2 sample problems. Sample Problem #1: What must the mass of the sphere be in order for the lever to remain perfectly balanced? Begin by determining F1 and D1. Because we are dealing with masses on both sides, F1 and F2 are actually the masses, but this does not matter. The answer will be the same in either case. So, F1 = 150 and D1 = 3 meters. The D2 value is 5 meters, and the F2 value is unknown. Thus we have: (150)(3) = (?)(5). Finishing the calculation, and you have 450/5 = 90 lbs. So, if the purple ball is 90 lbs, it will be in equilibrium with the green rectangle of 150 lbs. Sample Problem #2: What must the mass of the rectangle be in order for the lever to remain perfectly balanced? Again, first start with what you have been given from the graphic. What do we know? F1 = unknown D1 = 2 meters F2 = 100 kg D2 = 4 meters Once you have your data organized, simply plug this data into the formula, and solve! (F1)(2) = (100)(4) This yields: F1 = (100)(4)/2 Therefore, F1 = 200 kg. If you want to check your work (which is usually a good idea), you will see this: (200)(2) = (100)(4). Your solution is correct! STEP FOUR: Getting to Know You Now it’s time to get back into the computer simulator to conduct some experiments using the lever. Click HERE to open the Lever Simulator and then click on the Game tab. Your Task: You must complete all four levels in the Game mode. By the end of this task you must have earned a minimum of 20 stars total for full credit. Once you have collected your 20+ stars, show your screen to the Instructor for credit. Comprehension Check-Up II 1.) What must the mass of the orange sphere be in order for the lever to remain perfectly balanced? Mass:_______kg 2.) Where must the green rectangle be placed in order for the lever to remain perfectly balanced? Distance:_______m 3.) What must the blue rectangle’s mass be in order for the lever to remain perfectly balanced? Mass:_______kg ANSWER BOX: For Instructor Use Only STEP TWO: Background Information MOTION, PIVOTS, WHEEL, PULLEY, WEDGE, SCREW, INCLINED, MULTIPLIERS, PIVOTS, EFFORT, LEVER, RESISTANCE COMPREHENSION CHECK-UP 2.) What are the six types of simple machines? LIST these below. Wheel & axle, pulley, inclined plane, wedge, screw, and lever 3.) “All levers involve a fixed point that …. This point is known as the fulcrum.” a. slides b. turns c. pivots d. bends ANSWER BOX: For Instructor Use Only COMPREHENSION CHECK-UP 4.) LABEL these common applications of the 3 levers. Each lever type is used twice. 5.) Say you wanted to increase the efficiency of your 1st class lever. You want to do more work using less force or energy. How could you do this? a. Increase the distance between the load and the fulcrum. b. Decrease the distance between the load and the force. c. Decrease the distance between the load and the fulcrum. d. Increase the distance between the force and the load. 6.) With a typical excavator, which part is largest lever on the machine? a. The bucket b. The boom c. The arm d. The counterweight 7.) Comprehension Check-Up II ANSWER KEY 1.) What must the mass of the orange sphere be in order for the lever to remain perfectly balanced? Mass: 300 kg 2.) Where must the green rectangle be placed in order for the lever to remain perfectly balanced? Distance: 4 m 3.) What must the blue rectangle’s mass be in order for the lever to remain perfectly balanced? Mass: 200 kg