lab writeup

29.3 – undeflected ball 25 cm – deflected ball 61.9 – targeted ball

You have a very good analysis and appear to have very good data.

However these distances are mean distances over several observations, so these are not raw data. The raw data should be reported (i.e., give all measurements).

You should also report the standard deviation of your measurements.

You ended up with more reported energy than you started with. This cannot happen, of course, but the discrepancy isn't so great that it can't be explained by uncertainties in your data. However those uncertainties cannot be assessed without the standard deviations and other considerations.

Insert that information into your original document and resend it, and we'll then move on to assess the uncertanties to see whether they explain the discrepancies.

Vertical fall after collision 92 cm Initial velocities = 0

By how much did the first ball change in the collision?

By how much did the second ball change?

Ball 1 before collision v1=29.3 cm/.43 sec = 68 cm/sec Ball 1 after v1 = 25 cm/.43sec= 58 cm/sec Ball 2 before = 0 Ball 2 after = 62cm/.43 sec=144 cm/sec

The velocity change of the first ball is v1-v1= 58-68 = -10 cm/sec The velocity change of the second ball is v2 – v2=144 cm/sec

Which ball is more massive?

The change in MV is the same for both since the magnitude of the change in V for the second ball is about 11 times that for the first, we conclude that the first ball has 11 times the mass of the first.

Does this ratio make sense for a steel ball of 25cm diameter and a glass ball of 18 cm diameter? The steel ball has both greater density and greater volume. How much greater is its volume?

(25mm/18mm)^3=12500/5800= 2.7

If the steel ball has 11 times the mass and 2.7 times the volume, then what is the ratio of densities of steel and glass. D=M/V =11/2.7= 4.07 times the density

The density of the steel ball is about 7.5 g/cm^3. So the mass of the steel ball is about 60 grams. Density ratio 11/1, then the marbles mass is about 5.5 grams.

KE before and after: Ball 1 before collision v1=29.3 cm/.43 sec = 68 cm/sec Ball 1 after v1 = 25 cm/.43sec= 58 cm/sec Ball 2 before = 0 Ball 2 after = 62cm/.43 sec=144 cm/sec KE ball 1 before 1/2mv^2 = ½(60)(68)^2 = 138,720 g/cm^2 = .13 Joules

KE of ball 1 after collision is 1/2mv^2 = ½(60)(58)^2 = 100,920 g/cm^2 = .10 Joules

KE of ball 2 before = 0 KE ball 2 after = ½(5.5)(144)^2 = 57,024 cm/sec^2 = .06 Joules

This gives us .13 J before and .16 J after collision.

We set up the experiment by placing elevating one ramp 5.6 cm on a level. The first ramp was 29.7 cm and the flat ramp was 30.5 cm. We repeated this experiment a second time by elevating the ramps with a strap.

1. What were the mean and standard deviation of the distances you observed? (To find the mean we calculated the central line and measured the distances away from it and divided by 5) (First square distances, find the mean of these results, then square root of mean of squared distances)

1st Marble undeflected 1st marble after collision 2nd marble after collision First Setup .32/.232 .36/.049 1.08/1.41 Second Setup .26/.212 .42/.056 1.64/1.58

How many trials did you make for each setup? 5 trials

According to your results does a significant difference occur when the entire ramp system is raised 1 mm relative to the target marble? No the data does not differ significantly in terms of the mean and standard deviation. Raising the elevation does cause the marbles to travel further whether they are deflected are not. In the second set up the balls traveled on average 2-3 cm further than without the elevation."