PC1221 Lab Report: The Force of Gravity
Wang Zhikai
A0080959N
Group A1
PC1221 Lab Report: The Force of Gravity
Wang Zhikai
A0080959N
Group A1
1
Objectives
To determine the wave behaviour of electrons.
To determine experimental values for the interatomic spacing of graphite via electron diffraction
patterns.
2
Introduction
When a cart slides down an inclined track, it’s acceleration in the direction of the xaxis is equal to
gsin
Ɵ
, where
g
is the gravitational force due to the Earth’s gravitational pull and
Ɵ
is the angle of
inclination of the track. When there is no interference and there is minimal friction between the track
and the cart, the mechanical energy E of the system will remain constant due to the principle of
conservation of mechanical energy. Mechanical energy consists of gravitational potential energy and
kinetic energy, and the sum of these two components will remain constant in an (approximately)
isolated system.
3
Methodology
Part A: Accelerated Motion due to Gravity
We elevated one end of the inclined track by 14 cm using the laboratory jack and measured the
elevation with a measuring tape. We then measured the distance between the two ends of the inclined
track and recorded this distance as
L
in Data Table 1. We positioned the two photogates on the inclined
track and recorded the distance between them as
d
. We placed a picket fence onto the top of the cart
and connected the photogates to the Smart Timer.
We held the cart steady near the top of the inclined track and released it such that it moved freely
through the photogates. We then recorded the velocities
v
1
and
v
2
, the velocities as the cart passes
through photogates 1 and 2 respectively. We repeated this four more times to obtain 5 sets of data. We
then lowered the elevation of the track by 1 cm and repeated the previous steps for a total of four
different heights.
Part B: Conservation of Mechanical Energy
We measured the mass of cart as
m
(kg) and also the height
H
(cm) of the elevation of the inclined
track. We then set up the Smart Timer and connected the photogates to the timer.
We held the cart steady near the top of the inclined track and released it such that it moved freely
through the photogates. We then recorded the velocities
v
1
and
v
2
, the velocities as the cart passes
through photogates 1 and 2 respectively.
We varied
m
by adding masses to the top of the cart and repeated the previous steps until we
obtained 3 sets of data. We then used the laboratory jack to adjust the height of the elevation of the
inclined track and repeated the previous steps until we had 3 sets of data each, for a total of three
different heights.
4
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 Spring '11
 Tan
 Friction, Mass, Potential Energy, Angle of inclination

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