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Transcript
```Name: _______________________________________ Block: ____________ Date: _____________
Conceptual Physics-Newton’s 2nd Law Lab
Mr. White
Newton’s 2nd Law Lab
OBJECTIVE

Students will investigate the relationship between Net force, Acceleration and Mass.
Background
Newton's second law relates the acceleration of an object to the force that produces it. This
experiment uses the gravitational force on a falling mass to propel a box with masses inside
across the table. During the experiment you will provide evidence that supports the
equation for Newton’s second law.
A net force must be applied to a mass to produce acceleration. Acceleration is a change in
velocity, a positive acceleration increases velocity (speeds up a mass), a negative
acceleration decreases velocity (slows down a mass). Acceleration is the rate of change of
velocity per second; it has units of meters/second per second or meters/second 2.
Newton's Second Law relates force, mass and acceleration.
a = F/m
or
F = ma
where: F is force in Newtons
m is mass in kilograms
a is acceleration in meters/sec2
Materials Per Lab Group



1 Dynamics Cart
1 Wireless Dynamics System (WDSS)
Different Masses




Digital Balance
Calculator
Pulley
Dynamics Cart Track
Name: _______________________________________ Block: ____________ Date: _____________
Conceptual Physics-Newton’s 2nd Law Lab
Mr. White
Pre-Lab Questions
1. What is the equation that represents Newton’s Second Law of Motion? ____________________
2. A student pulls on a wagon that has a constant mass, if the student pulls twice as hard on the wagon,
how will that affect the acceleration of the wagon?
______________________________________________________________________________
3. A small child is pushing a shopping cart that is empty. Their mother fills the cart with bottles of
water, increasing the mass of the cart three times its empty mass. How will this affect how fast the
child can accelerate the cart?
______________________________________________________________________________
4. Using any resource at your disposal, sketch a line graph that represents a DIRECT relationship and an
Inverse Relationship between variable.
Direct Relationship
5.
Inverse Relationship
Using your notes from UNIT 1, how can I use a Velocity – Time Graph to find the acceleration of an
object?
__________________________________________________________________________________
6. Draw a free body diagram of the forces acting on the cart and the hanging weight in the diagram
below. Assume that the cart is frictionless.
FBD for Mass 1
FBD for Mass 2
7. What force is responsible for making the cart accelerate in question 5?
__________________________________________________________________________________
Name: _______________________________________ Block: ____________ Date: _____________
Mr. White
Conceptual Physics-Newton’s 2nd Law Lab
Procedure Sheet
PART 1:
In this experiment you will investigate the relationship between MASS and ACCELERATION for a constant
FORCE.
1. Setup the Equipment.
a. Turn on the LabQuest.
b. Place the track on a level surface and connect the Motion Detector to the USB port of the
Labquest 2.
c. On the LabQuest, select the small Graph Icon at the top of the screen to change to the graph
window.
d. Show only the Velocity Graph.
i. Graph  Show Graph  Graph 2
e. Place the dynamics cart on the center of the track. If the cart begins to roll, adjust the feet
on the track to level it.
2. Take the cart to the digital balance and measure the mass of the cart. Record this value in the
observation table. This value must be record in KILOGRAMS.
3. Hang the 20 g. mass on the string. The weight of this mass will create a force to move the cart.
Using the equation for weight, calculate this force and record it in the observation table. You must
convert the 20 g mass to kilograms before putting it into the equation.
4. Pull the cart back so that when you release it and hold it in place.
5. Press Play on the Labquest. When you hear the “clicks” from the detector, release the cart. The
Labquest should begin showing the position and velocity data of the cart.
6. Collect the average acceleration of the cart by completing the following steps.
a. Highlight the region of the VELOCITY graph that is linear and
shows a constant positive acceleration. (See Figure 1).
b. Select the Analyze Menu  Curved Fit  Velocity
c. When the new window shows up, select “Linear” under the
“Choose Fit” tab.
d. Record the slope (m), this represents the average acceleration of
FIGURE 1
the cart.
7. Now place a 200 g mass on the cart. Record the new value of the mass in
the observation table.
8. Repeat the data collection for the acceleration.
9. Repeat the experiment adding 200 g to the cart each time until you have collected data for 4 total
trials.
Name: _______________________________________ Block: ____________ Date: _____________
Mr. White
Conceptual Physics-Newton’s 2nd Law Lab
PART 2:
In this experiment you will investigate the relationship between FORCE and ACCELERATION for a constant
MASS.
1. Record the mass of the cart in the observation table.
2. Hang the 10 g mass on the string. Calculate the weight on the string in Newtons and record this in
the observation table. Remember the mass must be in KILOGRAMS to use the weight equation.
3. Collect the acceleration of the cart the same way as you did in Part 1.
4. Repeat the experiment with the 20 g, 50 g and 100 g mass hanging on the string.
Name: _______________________________________ Block: ____________ Date: _____________
Conceptual Physics-Newton’s 2nd Law Lab
Mr. White
Observation and Data Collection Sheet
PART 1: OBSERVATION TABLE
Trial
Hanging
Weight (N)
Mass of Cart
(kg)
Average
Acceleration
1
2
3
4
PART 2:
OBSERAVTION TABLE
Trial
Mass of Cart
(kg)
Hanging Mass
(g)
1
10
2
20
3
50
4
100
Hanging Weight
(N)
Acceleration
(m/s2)
Name: _______________________________________ Block: ____________ Date: _____________
Conceptual Physics-Newton’s 2nd Law Lab
Mr. White
Data Analysis & Understanding Sheet
PART 1: Create a Line Graph that shows how acceleration is affected by the mass of the cart. Make sure you
graph included the following.
a. Title
b. Labels axis with the units of measurement.
c. An appropriate scale on the two axis.
Part 2: Create a Line graph to display how the force acting on the cart affect the carts acceleration.
Name: _______________________________________ Block: ____________ Date: _____________
Mr. White
Conceptual Physics-Newton’s 2nd Law Lab
Identify the Independent, Dependent and at least two Constants for the experiments done in this lab.
Part One:
Part Two:
I.V.
_________________________________________
I.V.
_________________________________________
D. V.
_______________________________________
D. V.
_______________________________________
Two Constants:
Two Constants:
_________________________________
_________________________________
________________________________
________________________________
Looking at the graph from the analysis of Experiment ONE, what happens to the acceleration of an object if
the mass of the object increases?
_____________________________________________________________________________________
Looking at the graph from the analysis of Experiment TWO, what happens to the acceleration of an object if
the force acting on the increases?
_____________________________________________________________________________________
Use your graph from Part 1 to answer the following question. Although we never tested having 500 g of mass
on the cart, theoretically what would have the acceleration of the cart have been?
_____________________________________________________________________________________
Use your graph from Part 2 to answer the following question. How much would the hanging weight need to
way to make the cart accelerate at 1.0 m/s2?
_____________________________________________________________________________________
Based off the relationships observed in this lab, if a small car (small mass) and a large truck (large mass) were
stopped at a red light, which vehicle’s engine must provides more force to make the vehicle accelerate?
____________________________________________________________________________________
Based off the relationships observed in this lab, two identical trucks were stopped at a red light (so the same
force of an engine), but truck one is pulling a trailer, which truck will accelerate faster when the light turns
green? The truck with the trailer or the one without the trailer?
_____________________________________________________________________________________
```
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