081027

Part A: 

Suspend a domino from each side of the pulley, using a single string.  The positive direction of motion for the system is taken to be the direction in which the system rotates in the counterclockwise direction. 

The system consists of the pulley wheel, the string and the dominoes.  We will assume that anytime the system moves without outside interference, its acceleration is constant.

Use a pendulum as your timer and a meter stick to measure distance.

If when released the system accelerates from rest without your help:

• Determine its acceleration. 
• Give the system a push to accelerate it in the opposite direction and determine its acceleration.

If the system does not accelerate from rest:

• Give the system a slight initial velocity in the positive direction, such that it comes to rest while accelerating uniformly.  Determine its acceleration.
• Repeat, this time giving the system a slight initial velocity in the negative direction.

According to your data, which domino appears to have the greater mass?

Add a paper clip to the domino you believe has the greater mass.  If you are unsure, you may add the paper clip to either domino.

Repeat the entire procedure.

From your results, how many times more massive than the paper clip is the system of two dominoes?

Part B:

The system consists of a ramp, a plastic bag containing dominoes, and a single domino attached by a thread to the bag and suspended from the end of the ramp by a light, low-friction pulley.

What is the maximum number of dominoes in the bag for which the sliding acceleration is in the same direction as the motion of the system when the single domino descends?  Call this number N_0.

• Determine the sliding acceleration in this case.
• Determine the sliding acceleration if an additional domino is added to the bag.
• If the slope of the ramp is increased to .10, with the ramp oriented so that the component of the dominoes’ weight is in the same direction as the tension force exerted by the thread on the bag, then what is the sliding acceleration of the bag when it contains N_0 dominoes? 
• Repeat the preceding, with slope .10, when the bag contains one additional domino.

Based on your results, assuming all dominoes to be of equal mass, what is the coefficient of friction between the bag and the ramp?

What is the minimum ramp slope such that a plastic bag containing dominoes will slide at nearly constant velocity down the ramp?

What is the minimum ramp slope such that a plastic bag containing dominoes, initially at rest, will without any additional force slide down the ramp?  What is the acceleration of the bag once it starts to slide?  What therefore is the difference between the kinetic and static friction between the bag and the ramp?

Part C:

Determine the horizontal range of a 25 mm (diameter) steel ball as it rolls down the grooved track and falls to the floor.  The grooved track is positioned on a tabletop and its slope relative to the tabletop is .03.  Take data sufficient to determine, with the greatest possible accuracy, the horizontal velocity of the ball during its fall.

Repeat for ramp slopes of .06 and .09.

From your data determine for each slope the velocity of the ball upon reaching the edge of the ramp, and its acceleration while on the ramp. 

• Physics 121 and 201 students may assume in their analysis that the initial velocity of the ball as it leaves the edge of the ramp is purely horizontal, though this is clearly not the case. 
• Physics 201 students will later make a first-order correction. 
• Any Physics 231 student performing this experiment may begin by making the same assumption, but will be expected to also perform an analysis based on the assumption that the initial velocity of the projectile is parallel to the ramp.

• Edge effects (arising from the fact that between reaching the edge of the ramp and the beginning of free fall the ball experiences normal and frictional forces which differ from those experienced while in contact with the ramp) are minimal at the velocities attained in this experiment and may be safely ignored.  Analysis of these forces is considered beyond the scope of these courses, except as a potential special project for the highest-performing university physics student.

Graph the acceleration of the ball versus slope of the ramp.  Fit the best possible straight line to your graph and determine its slope.