PhysicsLAB Lab
A Battering Ram

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In this experiment you will examine the recoil energy of a hoop cart as it strikes a barrier that has an ever-decreasing mass. You will need the following supplies:
 
• 1 eight-foot board
• 2 wooden blocks
• 6500 grams of slotted masses
• 1 meter stick
• 1 hoop cart
• 30 cm of masking tape
• 1 triple beam balance
 
In each trial you will release the hoop cart from a state of rest from the top of the incline plane and allow it to roll down the incline and strike the stationary wooden blocks that are positioned along the designed line.
 
 
Preliminary Data
 
Before you begin your trials, you must measure and record the following preliminary data:
 
 
mass of wooden blocks (in grams) 

mass of hoop cart (in grams) 

entire length of incline plane (in cm) 

height of highest edge of the bottom surface of the incline plane (in cm) 

release distance from top of incline plane to stationary wooden blocks (in cm) 

 
Experimental Data
 
Record the following information for each trial:
 
• the barrier's mass
• the rebound distance along the incline of the hoop cart
• the displacement of both edges of the wood blocks after the collision
 
You can use masking tape to mark the cart's rebound distance for each trial. Remember to return the cart to the same initial release position as well as the barrier to its designated impact position before beginning the next trial. It is also recommended that the slotted masses be placed symmetrically on the wooden blocks to insure the best possible collision results.
 
 
wooden barrier cart rebound
added mass left edge right edge av distance distance
(g) (cm) (cm) (cm) (cm)
Trial 1 - 6500
Trial 2 - 5500
Trial 3 - 4500
Trial 4 - 3500
Trial 5 - 2500
Trial 6 - 1500
Trial 7 - 500
Trial 8 - 0
 
 
Analysis
 
When you have completed your trials, open the EXCEL sheet titled 1-HoopCart.xls and fill in the cells that are highlighted in light green. Do NOT touch the cells that are highlighted in light yellow since they are pre-programmed to assist you in the analysis of your data. Save your file to your period folder as LastnameLastnameHoopCart.xls. Be careful that your data is in the requested unit of measure.
 
What is the filename of your graph?
 

What is the equation of your graph?
 

What is the correlation coefficient (R2) of your graph? 

Based on your spreadsheet, during which trial did the hoop cart lose the highest percentage of its initial KE?
 

Use data recorded during the experiment on the behavior of the wooden barrier to support your choice in the previous question.
 

During the experiment, when the mass of the barrier was doubled, was the recoil distance of the cart also doubled?
 
During what range of TOTAL barrier mass would you consider the cart's collision to have been an "elastic" collision? Explain your rationale.
 

At what mass ratio should the cart no longer rebound?
 
During the experiment, how did the force exerted on the barrier by the cart compare to the force the barrier exerted on the cart?
 
What would change during a collision if you replaced your hoop cart with a second cart that did not have a hoop but could bounce with the same coefficient of restitution?
 

Explain how the movement of the blocks would be affected if the cart’s hoop was removed and replaced with velcro so that the collision became completely inelastic.
 

Why do you think this experiment was preformed on an incline?
 

Refer to the following information for the next three questions.

Using your knowledge gained from this experiment, answer the following problem.
A golf ball is hurled at, and bounces from, a very massive bowling ball that is initially at rest.
 
 
How does the recoil speed of the golf ball compare to its original speed?
 
After the collision, which ball has the greater magnitude of momentum?
 
After the collision, which ball has the greater kinetic energy?
 


When you have completed this lab, make sure that you submit your results online as well as turn in your calculations/data and a copy of your EXCEL graph. Names are important!

 
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