Name: Extending Student (really wants that A)
Date:
Class:
How Force affects Acceleration
Introduction:
The purpose of the “Forced to Accelerate” lab was to find how the acceleration of a
skateboard is related to the force pulling it. The group hypothesized that the more force
applied to the cart, the higher the acceleration would be. The experimental variable in this lab
was the force applied to the skateboard. The group changed the force through each set of
trials. The dependent or responding variable was the time for the skateboard to travel one
meter, which was used to calculate acceleration. The control variables were distance the
skateboard traveled, the skateboard traveled on the same surface, and the measurement
devices. Newton’s second law was an important principle in this lab. Newton’s second law
states that the acceleration of an object depends on the mass of the object and the net force
acting on it. In this experiment the groups changed the net force acting on the skateboard thus
changing the acceleration. An important formula is F=MA, or force = mass x acceleration. This
can also be expressed by net force / mass = acceleration.
Materials and Procedure:
Materials
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skateboard
meter stick
string
stopwatch
masking tape
spring scale, 5-N
several bricks or other large mass(es)
Procedure
1.
2.
3.
Attach a loop of string to a skateboard. Place the bricks on the skateboard.
Using masking tape, mark off a one-meter distance on a level floor. Label one end “Start” and the other
“Finish.”
Attach a spring scale to the loop of string. Pull it so that you maintain a force of 2.0 N. Be sure to pull with
the scale straight out in front. Practice applying a steady force to the skateboard as it moves.
4.
Find the smallest force needed to pull the skateboard at a slow, constant speed. Do not accelerate the
skateboard. Record this force on the first line of the table.
5. Add 0.5 N to the force in Step 5. This will be enough to accelerate the skateboard. Record this force on the
second line of the table.
6. Have one of your partners hold the front edge of the skateboard at the starting line. Then pull on the
spring scale with the force you found in Step 6
7. When your partner says “Go” and releases the skateboard, maintain a constant force until the skateboard
reaches the finish line. A third partner should time how long it takes the skateboard to go from start to
finish. Record the time in the column labeled Trial 1.
8. Repeat Steps 7 and 8 twice more. Record your results in the columns labeled Trial 2 and Trial 3.
9. Repeat Steps 7, 8, and 9 using a force 1.0 N greater than the force you found in Step 5.
10. Repeat Steps 7, 8, and 9 twice more. Use forces that are 1.5 N and 2.0 N greater than the force you found
in Step 5.
Data:
Trial 1
Force (N) Time
Trial 2
Time
Trial 3
Time
Avg
Avg Time Speed
(s)
(m/s)
Final
Speed
(m/s)
Acceleration
(m/s²)
0.8
4.79
7.96
7.84
6.86
0.15
0.29
0.04
1.3
5.61
4.37
3.99
4.66
0.21
0.43
0.09
1.8
3.56
3.76
3.92
3.75
0.27
0.53
0.14
2.3
2.87
2.32
2.67
2.62
0.38
0.76
0.29
Figure 1: Raw Data and Calculations.
0.35
0.30
0.25
0.20
Acceleration
(m/s2 )
0.15
Series1
0.10
0.05
0.00
0
0.5
1
1.5
2
2.5
Force (N)
Figure 2: Force vs. Acceleration graph. As force increased, so did acceleration.
Analyze and Conclude:
You know the force for the acceleration of zero if one is pulling the skateboard at a
constant speed. When an object is traveling at a constant speed there will be no acceleration
because you are not increasing or decreasing speed.
Acceleration on the skateboard relates to the force on the skateboard because when
the force increases so does the acceleration. This supports the hypothesis. This is supported by
the data in figure 1 and the graph in figure 2 because the graph curves up which means that
when the force increases so does the acceleration. This means that acceleration n an object
depends on how much force there is on an object.
Each trial, a person would keep pulling the cart at the same force in newtons. Also,
after each run/trial, there would be more mass put on or mass taken off the cart. Instead of
the force being the experimental variable, the mass of the cart would be. If you are pulling the
cart at the same force each time, the acceleration would decrease because if the cart was
getting heavier, it would take more time to pull if the force stayed the same through all trial
runs. Force stays the same, acceleration decreases. The friction could partially affect if you are
pulling with the same force each time. It may be off by 0.01N, for example. Also, all the
materials are already there.