Lab 7
Lab Performed: October 23
rd
, 2007
Lab Due: October 30
th
, 2007
Section 13
Objective:
To demonstrate the different relations of KE & PE in different situations since the total
energy E is equal to KE+PE and they must accommodate each other so that E=KE+PE.
Description:
Section 3:
A tube with mass m is held a distance h above the photogate sensor and is dropped and its
velocity is measured as it passes through the photogate. The total energy of the start is
compared to the total energy as the tube passes through the photogate.
Section 4:
A mass of 100g is hung from a 30cm string tied to a horizontal rod and is used as
pendulum. The weight is pulled to one side and let go where its velocity is measured by
the photogate sensor at the pendulum’s lowest point.
Section 5:
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View Full DocumentA vertical spring with a 500g weight is hanging from it. The mass is set into vertical
oscillatory motion and its position is measured as a function of time by a motion sensor.
The total energy is compared at different points in the motion.
Theory:
Section 3:
The total energy E is equal to
mgh
at the time of dropping the tube while the total energy
while the tube passes through the photogate beam is (1/2)mv
2
. Making
mgh
=(1/2)mv
2
leads to v=√(2gh).
Section 4:
The pendulum starts as PE and is gradually converted to KE as the pendulum falls down.
This is because PE=mgh and since h decreases as the pendulum falls, the PE is converted
to KE since Mgh= ½ Mv
2
as the path of the pendulum is circular, and the v= √(2gh).
Section 5:
In this section, y is determined to be the vertical coordinate where up is positive where
the coordinate gives the position of the end of the string from which mass m is hung. The
PE is calculated to be ½ ky
2
where k is the spring constant. With the PE being zero when
the spring is unattached (y=0) the gravitational PE for m is mgy, which will be negative
since y will be negative. When the end of the spring is at a point given b y and has a
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 Fall '08
 Adler
 Physics, Energy, Kinetic Energy, Mass, 5 kg, 04m, mgh

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