1101
Experiment:
Roll a steel ball down a 2-foot ramp, onto a level ramp and off the edge of the table to some level between table and floor. Incline the ramp the same as everyone else's ramp, using 2 marble blocks to support one end of the ramp, with the other resting on a dime which is placed on the tabletop.
Determine the average horizontal velocity of the falling projectile.
Comparing your results with those obtained by others for whom the distance of fall was different, test the hypothesis that the horizontal velocity of the freely-falling ball is constant.
Write up your results and explain the following:
Why it took most of the class over 20 minutes to figure out the horizontal velocity once they got their data
Why it should not have taken this long. Be specific, with references to class notes, Introductory Problem Sets, stuff you should have memorized, assigned text reading and assigned text problems.
Experiment:
Place a steel ball on a shelf-standard ramp. Slope the ramp at least slightly. Place a magnet with one of its poles facing down the ramp.
Move the steel ball slowly toward the ramp. Not the proximity of the ball to the ramp at the point where the ball first accelerates toward the magnet.
For each slope:
Determine the gravitational force component down the ramp as a multiple of the mass of the ball.
Assuming ball diameter 2.5 cm and density 7.5 grams / cm^3, determine the force exerted by the magnet on the ball.
Plot the slope of the ramp vs. the proximity of the ball to the magnet.
Plot the force on the ball vs. its proximity to the magnet.
Plot the acceleration the ball would experience on a constant-velocity ramp vs. its proximity to the magnet.
Answer the following, assuming that the ball is on a constant-velocity ramp of infinite length, based on your best interpretation of your
If the ball was released from rest at a distance of 4 cm from the magnet, how fast would it be moving when it reaches the point 3 cm from the magnet?
If the ball was released from rest at a distance of 3 cm from the magnet, how fast would it be moving when it reaches the point 2 cm from the magnet?
If the ball was released from rest at a distance of 2 cm from the magnet, how fast would it be moving when it reaches the point 1 cm from the magnet?
If the ball wa released from rest at a distance of 4 cm from the magnet, based on your previous answers, how fast would it be moving when it reaches a point 1 cm from the magnet?
If the ball was 1 cm from the magnet, how much velocity would it have to be given away from the magnet in order to 'coast' to a distance of 4 cm before turning around and 'falling' back toward the magnet?
If the ball is 1 cm from the magnet, is it possible to give it enough initial velocity so that it moves away from the magnet, never coming back?
Questions from University Physics Students:
For the experiment we are working on in university physics-- the one where we are supposed to find the horizontal displacement of the steel ball w/out redirecting to horizontal and find what slope is needed to make the ball land 3cm closer to the direct drop point-- are we supposed to find the slope needed to get 3cm closer without redirecting to horizontal or with redirecting to horizontal?
The problem is to find the slope without redirecting the ball.
Of course if you can’t do that, it wouldn’t hurt to first find the slope required for the redirected ball. That would give you some techniques that would be useful in the given problem, and help you understand the problem better.
Remember, it’s often a good strategy to solve a simpler problem before solving a more complex one.
For the PHY241 experiment, I am having trouble getting the horizontal velocity as the ball leaves the table after being directed to horizontal. I know that a=0 and the 'ds on the floor is 30cm. Also the Rise of the ramp is 9.5 cm and the run is 60cm. What equation(s) am I supposed to use to find this? We said this velocity would be somewhere around 70 or 72 cm/s.
Second, to predict how far the projectile would travel if not redirected to horizontal, would I use vx= v cos('theta) to find its velocity at the 189 degree angle?
See if you can answer the following questions, and if not, at what precise point you run into difficulty. If you email me this evening I’ll likely be able to answer further; otherwise we’ll get to it in class.
The tabletop is 94 cm above the floor. When the ball is redirected to horizontal its initial vertical velocity is zero, so its vertical motion is identical to that of a ball dropped from rest at that point. So how long does it take the ball to get to the floor? If necessary identify which of the variables `ds, v0, vf, a and `dt you know for the vertical motion, and figure out which equation(s) you would need to use to get your result.
Based on the 30 cm horizontal range, assuming horizontal acceleration 0 determine the initial horizontal velocity. The `dt is the same as for the vertical motion. Again if necessary identify the variables you know, and which equation(s) would be necessary to answer the question.
Assuming no significant change in speed when the ball is redirected to horizontal, the speed of the ball at the end of the ramp will be the same as the initial horizontal velocity you just found, whether the velocity is redirected to horizontal or not.
When not directed to horizontal, this velocity is directed at 189 degrees. So what are the x and y components of the velocity at the end of the ramp?
Which of the variables `ds, v0, vf, a and `dt do you therefore know for the vertical motion? Which equation(s) you would need to use to get the time of fall?
Once you have the time of fall which variables do you know for the horizontal motion? Which equation(s) would you use to get the horizontal displacement? What is your result?
How does this result compare with the horizontal displacement you actually observed?