Newton's Second Law

Block 6, Rebecca Harvey, Blossom Wong, Anthony R
make sure you publish!!
Pre-Lab: In the pre-lab demo, Ms. Freudenberg pulled Erin down the hall with constant force, and Erin dropped sugar packets at a constant rate. This showed greater distance between the packets as she got faster. This shows that a constant pull will create constant acceleration. Ms. Freudenberg then pulled with a greater constant force. This equaled a greater acceleration, showing that the the strength of the constant pull and the acceleration are directly related. Ms. Freudenberg then pulled both Erin and Shannah at the same time with a constant force, and the acceleration was smaller. This shows that acceleration and mass are indirectly related.

Purpose: In our lab, our purpose was to find how the force of the pull affected the acceleration. In order to do this, our independent variable was the force of the pull, our dependent variable was the acceleration, and the variable we held constant was the mass. and what else?

Procedure:

1. Set up a motion sensor on one end of a table.
2. Place cart wheel side up in front of motion sensor. Attach spring scale onto cart.
3. Place two 500g weights (constant mass) on top of cart to create constant friction. 
4. Pull spring scale at 4 Newtons constantly for first trial. Account for a force of friction of 3.5, and calculate acceleration from slope of the graph of motion sensor.
5. Pull spring at 6 Newtons constantly for second trial. Calculate acceleration keeping friction in mind.
6. Pull spring scale at 8 Newtons constantly. Calculate acceleration keeping friction in mind.
7. Pull spring scale at 10 Newtons constantly. Calculate acceleration keeping friction in mind.

Graph:

Verbal Model: As the force of pull increases, the acceleration increases proportionally.I think you variable was actually net force right - didn't you subtract off the fricition?

Math model: Acceleration = 0.614 m/s/s/N (Force of the Pull) - 0.057 m/s/s

Slope: The slope is an indication of how the force of the pull affect the acceleration. As the force of the pull increases by 1 N, the Acceleration increases by 0.6 m/s/s. The slope is representing the mass as a constant, except because the force affects the acceleration, the slope is actually the reciprocal of the mass.

Y-Intercept: close enough to zero to be negligible. Should be zero because when there is no net force pull, there is no acceleration.

The slope of the graph is equal to the reciprocal of the mass, which in our case is kept constant. Its equation is 1/kg. The y-intercept is a representation of the acceleration when there is no force of pull. The equation showing the relationship between acceleration, mass, and net force is:

Fnet = ma

This was derived from a force vs. acceleration graph which gave us:

Fp = ma + Ff
Fp - Ff = ma

The force of friction subtracted from the force of the pull is equal to the net force, which gave us our equation. This means that the force is directly proportionate to both the mass and acceleration, while mass and acceleration are inversely related.

For instance, the harder I push my brother on his bike, the more he accelerates, because the more force I apply, the acceleration directly increases. However, when I push my sister on her bike, she is much heavier than my brother, so the heavier she is, the less acceleration there is with the same pushing force. This is because mass and acceleration are indirectly related, with more mass equaling less acceleration and less mass equaling more acceleration.

Some sources of error include our immense force of friction because of the cart being on its back, which was difficult to measure and accurately account for. The angle of the spring scale measuring the force might have affected the data, as well as motion detector malfunctions; sometimes the cart was out of range of the sensor and that might have messed up the data. In the data itself, we might have included some data that was not related because we cropped only a certain portion of data on the screen. and how did you end up accounting for the friction?  That is an important part of the story!

Some suggestions include not placing the cart on its back but rather using the wheels to get rid of the friction as a factor in the lab. We could fix the angle of the spring scale as well, by using a protractor to make sure the angle is 90 degrees.

feedback?