Download answers exam 1 - University of Louisville Physics

NAME:
Section:
01(Th 10-10:50)
02(Th 1-1:50)
04(T 1-1:50)
05(Th11-11:50)
03(T 12-12:50)
Mid-Term Exam 1 - PHYS 298
Mendes, Spring 2015, Sept 25
Start time: 10:00 a.m.
End time: 10:50 am
- Calculators allowed; no other electronic device allowed
- You can use during the test the reference card that you prepared (a single
sheet of paper, double-sided, 8.5"×11")
- Absolutely no transfer of any sort of material during the test
- In solving the questions, show all the steps of your work and clearly state
your final answer
- Where it is appropriate, make sure to provide physical units to your
numerical answer
- If needed, consider g = 9.8 m/s2
1/10
(7 + 7 + 8 = 22 points)
1) Given two vectors:
2.00 ̂
3.00 ̂
4.00
and
3.00 ̂
1.00 ̂
3.00 ,
do the following:
a) Find the magnitude of each vector.
b) Write an expression for the vector difference
c) Find the scalar product
∙
2/10
using unit vectors.
3/10
(6 + 6 + 6 + 7 = 25 points)
2) A test car travels in a straight line along the x-axis. The graph below
shows the car’s position as a function of time. Answer the following
questions:
a) What is the instantaneous velocity at time
1 ?
b) What is the instantaneous velocity at time
4 ?
c) What is the average velocity for the time interval between
4 ?
d) What is the instantaneous acceleration at time
4/10
8 ?
1
and
5/10
(6 + 6 + 6 + 7 = 25 points)
3) Two crates, one with mass 4.00 kg and the other with mass 6.00 kg sit on
the frictionless surface of a frozen pond, connected by a light rope (see
Figure below).
A woman wearing golf shoes (so she can get traction on the ice) pulls
horizontally on the 6.00-kg crate with a force F that gives the crate an
acceleration of 5.00 m/s2
a) What is the acceleration of the 4.00-kg crate?
b) Draw a free-body diagram for the 4.00-kg crate. Use that diagram and
Newton’s second law to find the tension T in the rope that connects the two
crates.
c) Draw a free body diagram for the 6.00-kg crate. What is the direction of
the net force on the 6.00-kg crate?
d) Use part (c) and Newton’s second law to calculate the magnitude of the
force F.
6/10
7/10
(7 + 7 + 7 + 7 = 28 points)
4) A tennis ball is thrown with an initial velocity described an upward
component of 10 m/s and a horizontal component of 20 m/s. Consider that
air resistance is negligible for this tennis ball.
a) How much time is required for the tennis ball to reach the highest point of
the trajectory?
b) How high is this point?
c) How much time (after it is thrown) is required for the ball to return to its
original level?
d) How far has the ball traveled horizontally during this time interval?
8/10
9/10
10/10