Mini LAB pascal's principle
Blaise Pascal (1623-1662) is well known as a mathematician. Pascal also had a strong interest in physical events and spent much of his time trying to explain the phenomena he witnesses in hi experiments. He performed many experiments involving pressure in liquids. One of the most important principles he discovered became known as
Pascal's law or Pascal's rule.
INTRODUCTION - fill the blank for full credit
transmitted - hydraulics - area - incompressible- distance - force
Pressure is the _____________ per unit _______________.
Pascal's rules states that pressure applied anywhere in a fluid causes a pressure to be __________________ equally in all directions.
This is the result of fluids being _________________. If the pressure in a fluid is constant , the force per unit area is constant, so the larger the surface ______ the pressure is in contact, the larger the force. The smaller the surface area, the smaller the _________.
By arranging liquid columns of different sizes Pascal discovered that a relatively small force could lift a very heavy load
Pascal's law serves as the basis for the development of much of what is now known as ____________ .
Hydraulic jacks are used to lift heavy load.
In this hydraulic system, 2 syringes are connected by a tube. The system is filled with water.
The syringe on the left has a smaller area and the syringe on the right has a larger area.
A small force on the left can be used to lift a large weight.
Of course , since the machine increase your effort, there is a price to pay.
The _______________ the left syringe moves is larger than the ______________ the load moves.
If the load is 3 times larger than the effort, the ___________ you have to push is also
3 times larger.
In this lab, we will investigate such a system./
PART1: PLAY WITH THE SYSTEM ABOVE. (model for hydraulic jack)
You should have 3 or 4 syringes. The output one with a given output area. (should be large area). The load (a heavy Physics book)
should be place on this output area. Then you will try to lift the book with an input syringe of difference areas. (your push is your effort).
Report your observations:
is it easier to lift the book with a small area input syringe or with the large area one ?
What is the price to pay ? Explain below in details.
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PART 2: THUMB WARS !!! be nice with the material, do not squirt each other. I will ask you to leave if you play with water.
STEP1: First build a hydraulic system made of 2 identical 3ml syringes. You need fill each syringe, half way, with water.
Before connecting the syringes, Hold the syringe straight up and expell the bubbles of air.
Connect the 2 syringes together. ( instructions to follow). You are going to have a thumb war/
The winner is the strongest of the group. Winner : ______________________.
STEP2: Build now a 1ml/20ml system (see Step 2). The winner shoud take the 20ml side. The others 1ml side.
Who is winning now ? __________________What happened (in term of Pascal's law) __________________________________________
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STEP3 : build 3ml / 3ml system again and secure it to the table using a C-clamp.
Try to move a big fat Physics book with the system. Push the plunger all the way. Is it hard ?________________________
Do the experiment again but that time record with a ruler and a tape the distance the book moved while pushing the plunger all the way. _____________________________
STEP4: REpeat the exercice with the 1ml / 20ml system. The 20ml side is pushing the book. Push the plunger all the way. Is it easier ? ________
Note the distance the book moved___________________________________________
. conclusion? _____________________________________
ANALYSIS
1) What did you learn?
GOING FURTHER try without hints
1) What pressure (in lb/in2) is exerted on the ground by a 2,500 lb buffalo if each hoof has
an area of 4 in2 ?
hint: a buffalo is a mammal and as any mammal it has 4 legs. pressure = weight / (total area)
2) Consider a hydraulic jack. A 20N force (F1) is exerted on the small piston of the system. The cross-sectional of the small piston is 5 10-2 m2 (A1).
A) What is the magnitude of the weight (F2) that can be lifted by the large piston, which has a surface of 10-1 m2 (A2) ?
hint: F2/F1 = A2/A1
B) Find the mass (kg) of the load.
hint: F2 = weight = mass x 910
3) In a small machine shop, a hydraulic lift is used to raise heavy equipment for repairs and maintenance. The system has a small piston with cross-sectional
of 7.0 10-2m2 (A1) and a large piston of 2.1 10-1 m2 (A2). An engine weighting 2.7 103 N (F2) is resting on the larger piston.
A) What force must be applied to the small piston in order to lift the engine ?(solve for F1)
(F2/F1 = A2/A1)
B) The force F2 is _________ times larger than F1.
C) so the distance D1 you have to pump will be ________ times larger then D2 the distance the car will rise. This is the price to pay. (hint: same as in B).
So D2/D1 = F2/F1= ________.
D)So using C), If the engine rose 0.2 m (that is D2) , how far the did the small piston move ?
(you are solving for D1, the distance you need to pump).
4) Consider again a hydraulic jack. If a force of 50N (F1) is applied to the small piston
A) calculate the pressure P produced in the oil just below the small piston. The area of the small piston A1 is 2 cm2.
hint: pressure = force /area . convert cm2 into m2 fist. 1cm2 = 0.0001m2
B) what is the pressure exerted on the large piston. (Pascal's principle, the pressure is transmitted unchanged from the small to the large area).
C) calculate the upward force, F2, acting on the large piston.The area A2 of the large piston is 100cm2.
hint: force = pressure x area = P x A2 convert A2 into m2 first. (fdivide by 10,000)
D) The force F2 is _________ times larger than F1. so the mechanical advantage of the machine
is ________. (same number). So the distance D1 you have to pump has to be _________ larger than the distance the large piston moves. (same number).
E) use D). If the small piston moves down a distance of 5cm , how far upwards does the large piston move ?
hint: D1/D2 was given by question D).