Lab 6.2 Newton’s Second Law, F=ma
Name ______________
Purpose: To investigate the relationship among mass, force, and acceleration.
Required Equipment/Supplies: Skateboards, Spring scales, Timers
Discussion: All of us have felt the acceleration of a car as it leaves a stop sign or the negative acceleration when it comes to a stop.
We hear sportscasters describe a running back as accelerating through the defensive line. In this activity you will investigate some
variables that influence acceleration.
Procedure:
1. Distances of 5 m and 10 m have been marked off for you..
2. One student stands on the skateboard at the start line. Another student should stand behind the skater to protect the skater
from falling when pulled. The skater holds a spring scale by its hook. A third student must grasp the other end of the spring scale
and exert a constant pulling force on the skater. The puller must maintain a constant force throughout the distance the skater is
pulled. Do not pull harder to “get going.” Maybe the student behind the skater could give a slight push to get the skater going.
3. Time how long it takes to get to 5 m. Record this data in Data Table 1 along with the reading on the spring scale.
4. Repeat the experiment for the 10 m distance.
5. Repeat the experiment two more times, using different skaters to vary the mass. Record this data in Data Table 1.
Data Table 1
Person 1
m = _____ kg
Person 2
m = _____ kg
Person 3
m = _____ kg
Distance (m)
5
Force (N)
Time (s)
10
5
10
5
10
Calculations
1. We will attempt to calculate the acceleration of each trial, using two methods:
Method 1: d = vit + ½ at2
Method 2: F = ma
(initial velocity of 0 m/s)
(Force measured on scale)
(know the time and dist)
(mass of skater and board)
Solve for a!
Solve for a!
Skateboard = 5 kg
Your mass: 1 pound = 0.45 kg
Show your work below for both methods! Record in Calculations Table.
Calculations Table
Trial
#1
Distance
(m)
5
Method #1
Acceleration (m/s2)
Method #2
Acceleration (m/s2)
10
#2
5
10
#3
5
10
Questions:
1. Until the time of Galileo and Newton, people believed that a constant force is required to produce a constant speed.
Do your observations confirm or reject this notion?
2. What happens to the speed as you proceed farther and farther along the measured distances?
3. If you apply a constant force, what happens to the acceleration as you proceed farther and farther along the measured distances?
4. When the force is the same, how does the acceleration depend upon the mass?
5. When the mass of the skater is the same, how does the acceleration depend upon the force?
6. Suppose a 3 N force is applied to the skater and no movement results. How can this be explained?