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MAPÚA UNIVERSITY
Department of Physics
PHYSICS 1
EXPERIMENT NO. 3
NEWTON’S LAWS OF MOTION
NAME : ________________________________________________
STUDENT NUMBER : ____________ PROGRAM : ____________
COURSE & SECTION : ____________ GROUP NUMBER : ____________
DATE PERFORMED : ____________ DATE SUBMITTED : ____________
_________________________________________
INSTRUCTOR
- Is the report in correct format, well presented and neat?
- Is there an interpretation of results and qualitative observations in the analysis?
- Are the implications of results and sources of errors well discussed?
- Are there strong ties between the purpose statement and the results reflected in the conclusion?
Total
Deduction
Individual Report Grade
Group Report Grade
Report Grade
10 – exceeds expectation 8 – meets expectation 6 – approaches expectations 4 – falls below expectation 2 – does not meet expectation 0 – does not do anything
Experiment No. 3
Newton’s Laws of Motion
Experimental Goals
Identify the condition required for the cart to stay at rest while two forces are
applied on it.
Calculate the acceleration of the cart.
Investigate the relationship between the force applied on the cart, its mass, and its
acceleration.
Equipment
1 piece Dynamics Track
1 piece Dynamics Cart
2 pieces Photogates
1 piece Smart Timer
2 pieces Photogate Mounting Bracket
1 piece Smart Timer Picket Fence
2 pieces Super Pulley
2 pieces Mass Hanger
1 set Weights
2 pieces Strings (1 meter)
1 piece digital balance
Familiarization of Apparatus
In doing experiments, you should know how to use your apparatus properly.
In your own words, provide the use of the following apparatus you will be using in this
experiment:
Dynamics Cart
Dynamics Track
Photogate
Photogate Mounting Bracket
Smart Timer
Picket Fence
Super Pulley
Mass Hanger
Weights
Digital Balance
Vocabulary
In doing the experiments, you should know the definitions of the quantities you will
encounter in the experiments. In your own words, define the following:
Law of Inertia
Inertia
Law of Acceleration
Law of Interaction
Mass
Force
In Figure 1, the cart of mass m 1 is accelerating due to the tension T. From Newton’s second
law
T m 1 a
The hanging mass m 2 is also accelerating with the same acceleration due to the net force m 2 a
on it.
m (^) 2 a m 2 g T T m 2 g m 2 a
Equating the tensions
m 1 a m 2 g m 2 a m 1 a m 2 a m 2 g m 1 (^) m 2 a m 2 g
1 2
2
m m
mg
a
(eqn. 5)
This acceleration is the same acceleration described in the kinematics equation
2
t
s
a ^ (eqn. 6)
for a body starting from rest, s is the distance traveled by the cart and t is the time of travel.
Law of Interaction
When body A exerts a force on body B, then body B exerts an equal force in opposite direction on body A.
Procedure
A. Law of Inertia
- Attach the strings at the two ends of the cart and the super pulleys at the opposite ends of the track.
- Set the cart in the middle of the track. (Take note of the Cartesian Plane System where the left side from the cart is negative x-axis and the right side from the cart is positive x-axis.)
- Place the strings over the pulleys and attach the mass hangers at the end of the strings (one on each side).
- Place a certain amount of mass in the first mass hanger ( mA ) and in the second mass hanger ( mB ) that will leave the cart at rest in the middle of the track. (Caution do not exceed 200 g).
- Repeat procedures 1-4 for four more trials for different set of weights.
- Calculate the forces using
F mg
- Calculate the net force acting of the cart using
F^ FA FB
B- Part I. Constant Mass, Increasing Net Force
- Weigh the cart. Attach the super pulley at one end of the track.
- Attach the string at one end of the cart, place the string over the pulley and attach the mass hanger at the end of the string.
- Place the cart before photogate 1.
- Place photogate 2 at your desired final position.
- Set the mode of the smart timer to measure TIME, TWO GATES.
- Press button 3 of the timer to restart.
- Place a certain amount of mass in the mass hanger that will set the cart in accelerated motion. (Caution do not exceed 200 g).
- Repeat procedures 5-7 for three more trials, add weights on the hanger.
- Calculate the net force using
F net mBg
- Calculate the acceleration for each trial using equation 5 and 6.
B-Part II. Constant Net Force, Increasing Mass
- Weigh the cart. Attach the super pulley at one end of the track.
- Attach the string at one end of the cart, place the string over the pulley and attach the mass hanger at the end of the string.
- Place the cart before photogate 1.
- Place photogate 2 at your desired final position.
- Set the mode of the smart timer to measure TIME, TWO GATES.
- Press button 3 of the timer to restart.
- Place a certain amount of mass in the mass hanger that will set the cart in accelerated motion. (Caution do not exceed to 200 g).
- Repeat procedures 5-7 for three more trials, add weights on the cart.
- Calculate the net force using
F net mBg
- Calculate the acceleration for each trial using equation 5 and 6.
Experiment Set Up B
Guide Questions and Problems
- In Part A, describe what happened to the cart as two different masses were placed on the mass hangers. For the cart to stay at rest, what sets of forces did you apply on the cart for each trial? What is the net force exerted on the cart for each trial?
- In B, Part I, how would you relate the acceleration of the cart to the total hanging weight if the mass of the cart is constant?
- In B, Part II, how would you relate the acceleration of the cart to its total mass if the hanging weight is constant?
PROBLEM
- If the mass of the cart in the experiment is 600g and the total hanging mass is 200g, how long will the cart travel a distance of 50 cm starting from rest?
Experiment No. 3 Newton’s Laws of Motion
Name: Date: Section: Group No:
Data Sheet
Table A. Law of Inertia
trials
mass A ( mA ) (kg)
force A ( FA ) (N)
mass B ( mB ) (kg)
force B ( FB ) (N)
net force
( Fnet )
(N)
Table B. Law of Acceleration
Part I. Constant Mass, Increasing Net Force
mass of the cart = ____________ kg
initial position ( xo )= __________ m final position ( xf )= __________ m
trials
total mass, hanger ( mB ) (kg)
net force
( Fnet )
(N)
time of travel ( t ) (s)
acceleration ( a ) (m/s^2 ) computed experimental 1 2 3 4
