Enzyme, Pharmaceutical Aids, Miscellaneous Last Part of Chapter no 5th.pdf
PHYS 181 Physics For Scientists And Engineers II.docx
1. PHYS 181 Physics For Scientists And Engineers II
Answer:
Previously, you explored the motion of single objects (or objects attached by a string). As
you know, objects can interact with one another. When two objects collide, it is difficult to
calculate the force between them as a function of time. However, we can make use of linear
momentum to understand and describe their motion. The linear momentum of an object of
mass m moving with velocity v is given b
Linear momentum is a vector quantity that points in the same direction as an object’s
velocity. If we consider the change in linear momentum of an object (assuming its mass is
constant) with respect to time, we see that
So, the change in linear momentum per unit time is given by the net force on the object.
Therefore, if the net force is zero, the linear momentum remains constant.
You will soon study the case of two objects colliding. We will assume that during the
collision the only force acting on the objects is some force between them. Newton’s 3rd law
states that the force of the first object on the second matches the force of the second on the
first. This means that the net force on the system is still zero, so the total momentum must
remain constant. This means that while one object may slow down during a collision, the
other object may speed up.
The kinetic energy of an object (which you studied in the previous lab) does not necessary
remain constant between collisions. As an example, two cars could collide head-on and
come to a complete stop. In this case, all the kinetic energy was lost.
However, the total momentum was still conserved.
In this lab, you will create some collisions and observe the conservation of linear
momentum. The carts can undergo both nearly elastic (by use of a spring) or totally
inelastic (by use of VELCRO) collisions.
2. Goals Of This Lab:
Demonstrate linear momentum conservation for collisions
Compare elastic and inelastic collisions Measure energy loss in an inelastic collision Test
conservation of energy with an explosion.
Watch the lab tutorial video if you haven’t already, then open up the lab7.zip file in IOLab
for the instructions you should follow while taking your data.
After Taking Data:
You now have at least 9 measurements for the elastic collisions section (3 for each setup), 9
for the inelastic collision section (again, 3 per setup), and 6 for the ‘explosions’ section (3 for
each portion).
Here’s an example table of all required measurements/calculation for the Inelastic collision
portion of the lab.
m1(g)
m2(g)
v1initial
v1+2final
p1initial
p1final
6. Be sure to include every value that you are expected to calculate for each trial in your table.
Part – 1 : (Elastic Collision)
m1(g)
m2(g)
v1initial
v2initial
14. 0.0609
0.0380
Writing in the formal lab report style, be sure to address the following topics:
Consider each part of the lab separately. To within the uncertainty of your measurements,
was the momentum conserved? If not, how far from your predictions were your final
results? Explain.
Momentum is conserved in all 3 parts of the lab. As can be observed in the tables above,
pinitial = pfinal implying that the momentum is conserved.
Looking at your results for part 1’s ‘elastic’ collisions, was the energy actually conserved? If
not, how much was lost during the collision, and what could have caused that?
During the elastic collisions in part-1, the kinetic energy remained conserved as can be
observed in the data table ; KEinitial = KEfinal
Describe what happens when the remote has an elastic collision with the cart while their
masses are identical. What happens instead when the remote is much heavier than the cart?
When the masses are same, the momentum of the remote is transferred to the cart that was
initially at rest. In other words, the final velocity of the car is equal to the initial velocity of
the remote.
On the other hand, in case the remote is heavier than the mass, in that case, the final velocity
of the remote decreases and the final velocity of the cart increases.
Where does the energy that is lost go during an inelastic collision?
During inelastic collision, energy is lost in bonding the two bodies that were initially two
different bodies. In this case, the energy is lost in spring energy as well
How consistent were your spring energy measurements? What method did you find works
best to ensure repeatable results?
The spring energy measurements were consistent and gave the desired results.
15. Discuss any sources of error in your measurements.
While arranging the 1 dimension collision, the remote might be moving out of the line
before the collision. As a result, the motion didn’t remain 1-dimension, which leads to errors
in measurements. Secondly, the spring is not completely elastic which also leads to
measurements error. Air resistance and ground frictional forces are also there which we
didn’t consider.
