PHYSICS 221
EXPERIENCING NEWTON’S LAWS
This is a group write up. It must be word-processed. All graphs (which can be neatly drawn by hand) must be integrated into the text.
Part 1: How do you win at Tug O’ War?
“The following two statements are true. In Tug of War:
1. Each team pulls equally hard on the other.
2. The team that wins pushes harder on the ground.”
A. Get with another group and play a “safe” round of tug of war. Play on two different surfaces to check out different friction effects. (e.g. socks vs. shoes on the lab floor or grass vs. cement outside)
B. Consider each team as a unit. Draw a free body diagram of each team.
C. Refer specifically to the diagrams to write a paragraph discussing how the two statements above are true.
Part 2: The Mystery of Salami & Spring Scales
A. Below is a figure showing the three basics salami positions. If the Salami has a mass of 200 grams predict what will the scale read for each situation.
i. Hanging Salami - Scale Reading =
ii. Salami & the Wall - Scale Reading =
iii. Salami vs. Salami - Scale Reading =
B. Set up the three situations and record the scale reading.
C. Draw free body diagrams for the Salami(s) and the scale in each situation. (Ignore the weight of the scale.)
D. Write a paragraph explaining why the scale readings are what they are. Refer to your force diagrams.
Part 2: How to get that piece of paper stuck under that book?
A. Place a sheet of paper between your physics text and the table so that the entire book rests on the paper. Observe what happens when you pull fast on the sheet of paper and when you pull slowly on the sheet paper.
B. Draw a free body diagram for the book
C. Write a paragraph explaining the difference between the two situations.
Part 3: Measurin’ the G’s in an Elevator
A. Go to the elevator with your group, a spring bathroom scale, and a force plate. One person in the group will ride the elevator one time on the scale and a second time on the force plate. During the first ride, the others will read the bathroom scale and write down the data. During the second ride, they will record the data with the laptop computer (using LoggerPro). Before going to the elevator, ask me to show you how to set up the force plate with LoggerPro and the laptop computer.
The ride in the elevator will consist of going up from the second floor to the third floor, stopping on the third floor staying in the elevator, and then riding back down to the second floor.
B. Take the maximum/minimum scale readings while the elevator is doing the following:
i. not moving -
ii. starting upwards -
iii. going upwards -
iv. stopping upwards -
v. starting downwards -
vi. going downwards -
vii. stopping downwards -
C. Record the same complete same ride with the force plate.
D. Back in the lab, view the force plate measurements with LoggerPro. Make a free body diagram the person riding the scale in each situation.
E. Calculate the magnitude and direction of the net force on the person in each situation. Use the force plate readings, and check that they match the bathroom scale measurements.
F. Calculate the person’s mass from the data.
G. Calculate the person’s acceleration (magnitude & direction) in each situation.
H. Calculate the # of “g’s” the person experiences in each situation (= normal / weight).
I. Write a paragraph which connects the direction of the acceleration you’ve found using dynamics () to the definitions for acceleration we used in kinematics (slowing down in the positive direction, etc.).
Part 4: Fun with Balloons (to do outside of the lab hours)
A. Obtain from your local physics department a helium balloon
B. I recommend that you do the experiment on a bus. You can also do it in a car with all of its windows closed. But if you do it in a car, the driver should not be the person doing the experiment. You must make sure that the balloon doesn’t interfere with the driving of the car and that all safety rules are observed (seat belts, etc…). An empty parking lot would be best to do the experiment in a car.
C. Write down how the balloon reacts to the following situations:
i. Speed up fairly quickly.
ii. Slow down fairly quickly.
iii. Turn to the right in a circle.
iv. Turn to the left in a circle.
D. Write a paragraph which describes the results of your experiment and explains in terms of Newton’s first, second laws and air pressure differences why the balloon reacts as it does.