Group member names:
-Greg Strickler
-Won-Yong.Shin
-Chris Marino
Laboratory Activity 5: Force
and Motion
Objectives

Explore how force is related to acceleration and velocity.

Develop a quantitative understanding of the force relationship.

Learn about proportional and inversely proportional graphs.
Equipment

Computer

Cart masses

Ultrasonic motion sensor


Force sensor
Pulley to mount on end of
track

2 USB Links

String or fishing line

Dynamics cart

Wire hook for weights

Track for cart

Masses for hanging.
Activity One: Force and motion
Velocity
Acceleration
Prediction 1: Using the line tool on the drawing toolbar of Word, draw a line on
both the velocity, acceleration and force graphs below predicting the shape of a
curve for a cart starting at rest and being pulled with a constant force.
Time
Force
Time
Time
Set up the equipment: Obtain 2 USB Links, a force sensor and a motion
detector. Plug the USB links into the USB hub (small plastic black box) and plug
that into the computer and the power source. Open the experiment file called
MotionAndForce.ds to display force, acceleration and velocity graphs. You can
find it by going to the networked disk “PLAB” (usually disk G:), in that opening the
folder “Plab”, then finding the folder for Physics 201, and then looking in the
folder for Lab 4. Set the track on the table so one end is hanging off, place the
motion detector at the other end. Attach the pulley so that it is on the end off the
table. Attach the force sensor the cart on the magnet side by using the screw.
Make sure the screw goes through the hole labeled “cart” and not “IDL bracket.”
Hook the length of fishing line on the hook of the force sensor, run it over the
pulley, and hang the wire mass hook on the end. Place both of the black cart
masses on the cart.
Experiment: Place the cart on the track about 30 cm (1 foot) away from the
motion detector and turn it on, with one person holding it in position. Have
another team member start taking data. Let go of the cart as soon as the clicking
sound is heard, careful to not get any hands between the detector and the cart,
and let the cart speed away. Catch it just before it crashes into the other end of
the track. When you have a nice graph, copy the graph and paste it in the
section below.
Question 1: How did the result compare to your prediction? Explain how the
velocity, acceleration graphs are related.
The graphs matched our predictions. The velocity increase gradually will a
positive slope, force stayed constantly positive, and the it had little acceleration.
Experiment 2: Measure the average force and average acceleration of the cart
during the time it is moving freely. Do this by click-dragging a rectangle around
the data points with the mouse, and then selecting “mean” from the “Statistics”
button at the top of the window. Record the force and acceleration in the chart
below. Add masses to the wire hanger hanging at the other end of the string and
repeat.
Force (N)
Acceleration (m/s2)
Hanger alone
.172
.069
Hanger + 10 g
.224
.145
Hanger +20 g
.248
.377
Hanger +30 g
.329
.483
Hanger + 40 g
.425
.592
Then enter the force and acceleration data in the table in DataStudio. A graph of
Acceleration vs. force will be automatically created for you. Paste that in the
space below.
Question 2: How does the acceleration relate to force? Can you write down a
mathematical expression?
As force increases so does acceleration. F=ma.
Experiment 3: Repeat the previous experiment, except this time keep the mass
on the hanger the same and vary the mass of the cart. Using the scale in the
classroom, find out how much your cart weighs with the force sensor, and then
each cart mass. Place 10 or 20 grams on the hanger, and then take all the
masses off the cart. Do the experiment, recording the total mass of the cart and
the acceleration. Repeat for the cart + 1 mass, then with 2 masses, and so forth.
Share masses at your table if you need to.
Mass (kg)
Acceleration (m/s2)
Cart and force sensor
.35
.497
Cart, sensor & 1 mass
.6
.394
Cart, sensor & 2 mass
.85
.247
Cart, sensor & 3 mass
1.1
.169
Cart, sensor & 4 mass
1.35
.143
Then enter the force and acceleration data in the hidden table in DataStudio.
Look in the navigation window in the lower left corner, and click on the second
data table. A graph of Acceleration vs. Mass will be automatically created for you
in the third graph, which you will have to click on in the same navigation window.
Paste that in the space below.
Question 3: How does the mass relate to acceleration? Can you write down a
mathematical expression?
As mass increases on the cart, the acceleration decreases. F/m=a.
Summary
The following questions will help you get the main ideas out of this lab. You
should find these straightforward questions, but take the time to talk it over with
your team and write complete answers to these questions. You may find your
answers here to be the most useful part of this lab down the road.
Summary 1: Force is directly related to which of the motion quantities? How
does changing the force change its motion?
Acceleration. If you increase the force the acceleration increases and if you
decrease the force the acceleration decreases.
Summary 2: How does mass affect motion and force? Can you write down an
expression that relates force, mass and acceleration?
F=ma. The larger the mass, the more force needed to accelerate the object. If
the force is constant and mass is increased, acceleration will decrease.
Summary 3: How do you know your above statements are true? What
experimental observations and/or logical reasoning can you give to justify what
you said in summary questions 1&2?
We know our statements our true because of the experiments run in datastudio.