Elasticized Physics Lab
Elasticized Physics Lab

Purpose:  To find the relationship between force and constant acceleration, using elastics attached to crash carts kept at a constant force, and measuring dots on the ticker tape.  Limitations would include human inaccuracy because if we are not capable of keeping the meter stick at constant force it won’t give good data.  (As you can tell!) By using two different forces we can more accurately evaluate the data and a comparison of the graphs. 

Equipment: Ticker Timer, Ticker Tape, Scientific Rubber Bands, Crash Carts,
Tape, and Meter Stick

Procedure:
1. Tie One Elastic to the crash cart
2. Attach ticker tape to bumper of crash cart and run tape through ticker
timer.
3. Stretch Elastic band to 23 cm by hooking the loop to the meter stick and pulling it out in front of the crash cart.
4. Elastic and crash cart are to keep the desired stretch while running
the length.
5.  Repeat for 2,3,4,5 elastics and for 24 cm stretch for all amounts of
elastics.
6.  Count 6 dots in five consecutive sections and calculate the speed and
acceleration.

Data:  See attached sheet. 

Sample Calculations:
segment period = period (s) x 6 dots = 0.0167 x 6 dots
Calculating Velocity
v= d / t
v= displacement (cm) / segment period (s)
Velocity for one elastic at 23 cm
v = 11.5cm / 0.1s
   = 115 cm/s

Accelerations are the slopes of the velocity- time graphs. 

Table of Results:  See attached sheet. 

Sources of Error:
Friction in the wheel bearings of the crash cart would interfere with motion, as would friction from the air and table.  Get a frictionless cart and surface to fix this problem. 

If the elastics were not calibrated correctly then they would be different lengths and would bring undesired data.  Get better elastics or use good fish scales to fix this problem. 
Inaccurate measuring devices, meter sticks.  To fix problem get more accurate measuring devices with more graduations. 

Crash cart was not equal weight on both sides, this would pull it side to side instead of ahead.  To fix problem get better crash carts that are evenly weighted. 

Conclusion:
Although our data was not ideal the relationship between acceleration and force is a direct proportion.  We determined this because after removing really bad data points our best-fit lines were straight.  This relationship is known as Newton’s Second Law.