experiment 1 by bayot, lim, uy
TRANSCRIPT
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De La Salle UniversityCollege of Education
Science Education Department
PHY 583MEarth and Environmental Science
Experiment # 1
WORK AND KINETIC ENERGY
Members: Bayot, Joysol
Lim, Perlita
Uy, Roxanne
Prof: Dr. Cecil Galvez
Class Period: Sat, 8:00 am11:00 am
Date performed: 1/26/13
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I. INTRODUCTIONA. BACKGROUND INFORMATION/THEORY AND CONCEPTS
Work is the change in energy from one form to another by means of an external force.
When work is done on an object, the object is said to have either gained or lost a certain
amount of energy of a particular type. Hence the units of work are the same as the unitsof energy: joules. Work is considered to be positive, negative, or zero in value,
depending on the direction of transfer.
To calculate the work done, the distance travelled and the net force acting on the object
must be determined.
W = Fnet .d
Fnet = M.a
Change in kinetic energy states that the work done by the resultant external force on abody is equal to the change in the kinetic energy of the body.
KE = 1/2 Mv2
Wtotal=K = KfKi
The result is called Work-Kinetic energy theorem.
The purpose of this Activity is to calculate the work done by a constant force and to
compare the work done and the change in kinetic energy.
B. OBJECTIVES
This activity aims:
To examine and calculate the work done on the dynamics cart by a constantforce.
To compare the work done and the change in kinetic energy.C. HYPOTHESIS
If an external force is applied on a body with displacement, then a work is done.
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II. METHODSTART
SECURE MATERIALS
PREPARE SET-UP
USE SPARK COMPUTER PROGRAM
COLLECT DATA NEEDED FOR THE EXPERIMENT
GET THE ACCELERATION OF THE CART
CALCULATE WORK DONE
CALCULATE KINETIC ENERGY
IS THE DATA
COMPLETE
AND N
ACCURATE?
Y
FIX SET UP
MAKE FURTHER STUDIES
END
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III. Materials Used and experimental set-up
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IV. DATAa. OBSERVATIONS in a DATA TABLE or CHART
Table 1. Shows the hanging mass, minimum distance, maximum distance, and the distance
(difference between minimum and maximum distance) of the 3 runs of the cart
Table 2. Shows the hanging mass and the acceleration of the 3 runs of the cart
Table 3. Shows the hanging mass, distance, acceleration, force and work of the 3 runs of the cart
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Table 4. Shows the hanging mass and the acceleration of 3 runs of the cart
Table 5. Shows the hanging mass, distance, acceleration, force and work of the 3 runs of the cart
Table 6. Shows the hanging mass and the final velocity of the 3 runs of the cart
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Table 7. Shows the hanging mass, final velocity, work and change in kinetic energy of the 3 runs
of the cart
Table 8. Shows the mass of dynamic cart, hanging mass, distance, acceleration of the cart, and
the force of the 3 runs of the cart
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b. GRAPHS
Figure 1.Position versus Time of the 3 runs
Figure 2.Velocity versus Time of the 3 runs
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Figure 3.Force versus Hanging Mass of the 3 runs
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Figure 4.Work versus Force of the 3 runs
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Figure 5.Work versus Change in Kinetic Energy of the 3 runs
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c. CALCULATIONSc.1 Final Velocity
Vf = Vi + a * t
where:Vf = final velocityVi = initial velocity
t = change in time
a = acceleration
c.2 Force
f = m x a
where:
f = Forcem = massa = acceleration
c.3 Work
W= Fnet d = F cos
where:
Fnet = Net Forced = distance
c.4 Acceleration
a= v
t
where:
v = change in velocity
t = change in time
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c.5 Kinetic Energy
KE = mv 2
where:
KE= Kinetic energym = mass
v = velocity
V. ANALYSISBased from Figure 2, it shows that the velocity versus time graph moves along a
straight line, making it linear in shape and is constant. Given that it shows the slope of
velocity with respect to time, it represents the physical quantity of acceleration. It
also means that acceleration on the graph is constant
The initial kinetic energy of the cart is zero (0). Any object that is not in motion will
have an initial kinetic energy of zero.sa
Figure 3 shows that the graph moves along a straight line, thus making its shape a
linear one. The acceleration of an object depends on the net applied force, and the
mass. In this experiment, the hanging mass determines the net force acting on thesystem of both masses. This net force accelerates both the hanging mass and the
carts mass; the cart mass is accelerated horizontally, and the hanging mass isaccelerated downward.
Figure 4 shows that the graph shows a linear relationship between work and force.
Force is essential to perform work. When the point of application of the force getsdisplaced, then force is said to have performed work. Based on the graph and the
equation, W = Fnet . d, work is directly proportional to force.
Figure 5 shows a graph that is not linear in shape, due to some error that can be
anticipated while performing the experiment. However relationship between work
and change in kinetic energy is applicable when conservative forces act on a system.This relationship is known as the Work Energy Principle. So Work may be definedas a change in Kinetic Energy
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VI. CONCLUSIONWork done by applied force is equal to the product of F, the component of Fa in the
direction of the displacement, and change in d, the distance through which the mass
moves.
Theoretically work done must be equal to change in kinetic energy. But the results of
the activity/experiment would not yield the theoretical aspect since in the real setting
some forces cannot be neglected like friction.
VII. ANSWERS TO QUESTIONS1-2. Draw the cart and then indicate the forces acting on the cart. Which force/s does/ do
not work on the cart? Why?
Where:
Fnorm = normal force
Fgrav = gravitational force = M*g
Fapp = applied force (tension on the string) = m*g
fk = kinetic friction
3. In this experiment, 2 graphs were recorded. These are the position vs time graph, and
velocity vs time graph.
a.What are the shape of the position vs time graph and the velocity vs time graphThe graphs move along a straight line, thus making it linear in shape.
Fnorm
Fgrav
Fappfk
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b.What do these graphs tell you about the carts position, velocity, and acceleration as thecart moves from its initial position to the final position?
c.What physical quantity does the slope of the position vs time graph represents?The slope of position with respect to time represents velocity of the object.
d.What physical quantity does the slope of the velocity vs time graph represents?The slope of velocity with respect to time represents acceleration.
4. If you increase the hanging mass, what do you think will happen to the following
quantities?
a.Acceleration of the cartAcceleration of the cart will increase since there is an rise in pressure in order to move theobject.
b.The net force of the cartLike acceleration, net force will rise since there is an increase in the hanging mass.
c.The work done on the cartWork done will increase since variables affecting work increased.
d.The change in kinetic energy of the cartChange in kinetic energy will also increase because it is proportional to the rise of otherfactors.
5. What does it mean if the slope of the x vs y graph is equal to 1?
When the slope of the x vs y graph is equal to 1 it means that change in work done is equal to
change in kinetic energy.
6. What is the value of the slope of work vs KE graph? Is it really equal to 1? What does
it tell you about the relationship between work and KE?
Generally, the work done on a body is equivalent to the change in kinetic energy of that body.
Since the body is initially at rest, the kinetic energy of the dynamics cart depends only on itsfinal kinetic energy.
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The slope of the graph is equivalent to 1.16 using the formula, m= (y1-y2) / (x1-x2). The value
of the slope tells that there is a slight difference between the obtained work and the kinetic
energy. Based from the data, the shorter distance travelled by the cart with the 0.020 kg
hanging mass is the cause of the sudden decrease in final velocity hence, the decrease inkinetic energy.
7. What do you think is the reason why the work done and KE are not really equal to one
another?
Work done and change in kinetic energy are not equal to 1 since there are other variables to
consider when computing for it. It will only be equal to each other if these other variables
will be neglected.
VIII. REFERENCES1. Heuvelen. University Physics, 6
thedition. 2004
2. Young and Freedman. University Physics, 11th
edition. 2005
3. Hewitt. Conceptual Physics. 2005
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