Download Exam 1B #2

PHYS122
FALL 2005
EXAM #1
Monday Version
Name: _____________________________________________________
Problem 1 ____________________________________ (25 pts)
Problem 2 ____________________________________ (10 pts)
Problem 3 ____________________________________ (20 pts)
Problem 4 ____________________________________ (30 pts)
Problem 5 ____________________________________ (15 pts)
Problem 6 ____________________________________ (20 pts)
Problem 7 ____________________________________ (20 pts)
Problem 8 ____________________________________ (20 pts)
Problem 9 ____________________________________ (20 pts)
Problem 10 ___________________________________ (20 pts)
TOTAL Part B _______________________________ (200 pts)
1. The figure below shows a "conical pendulum", in which the bob (the small object at
the lower end of the cord) moves in a horizontal circle at constant speed. (The cord
sweeps out a cone as the bob rotates.) The bob has a mass of 0.040 kg, the string has
length L = 0.90 m and negligible mass, and the bob follows a circular path of
circumference 0.96 m.
A. Draw a free-body diagram for the bob
B. What is the tension in the string?
C. What is the period of the motion?
2. Snow is falling vertically at a constant speed of 8.0 m/s. At what angle from the
vertical do the snowflakes appear to the falling as viewed by the driver of a car
traveling on a straight, level road with a speed of 50 km/h?
3. The position of a 0.25 kg particle moving in an xy plane is given by
r = (2.00t3 -5.00t) i + (6.00 -7.00t4) j , with r in meters and t in seconds. For
t = 2.00 s, calculate in unit-vector notation
A. the position
B. velocity
C. acceleration
D. net external force acting upon the particle
4. Block B in the figure below weighs 730 N. The coefficient of static friction between
block and table is 0.28. Assume that the cord between B and the knot is horizontal.
A. Draw free body diagrams for block A, block B, and the knot
B. Find the maximum weight of block A for which the system will be stationary.
5. A hot-air balloon is ascending at the rate of 14 m/s and is 75 m above the ground when
a package is dropped over the side.
A. How long does the package take to reach the ground?
B. With what speed does it hit the ground?
6. In the figure below, a force F of magnitude 15 N is applied to a FedEx box of
mass m2 = 1.0 kg. The force is directed up a plane tilted by = 37°. The box is
connected by a cord to a UPS box of mass 3.0 kg on the floor. The floor, plane, and
pulley are frictionless, and the masses of the pulley and cord are negligible.
A. Draw free body diagrams for both blocks
B. What is the tension in the cord?
7. A 2.00 m tall basketball player wants to make a goal from 10.0 m from the basket, as
in Figure P3.58. If he shoots the ball at a 45.0° angle, at what initial speed must he
throw the basketball so that it goes through the hoop without striking the backboard?
8. Figure 5-57 gives, as a function of time t, the force component Fx that acts on a
4.00 kg ice block, which can move only along the x axis. At t = 0, the block is moving
in the positive direction of the axis, with a speed of 4.0 m/s.
A. What is the speed of the block at t = 8 s?
B. What is its direction of travel at this time?


C  - 3 î  4 ĵ  0 k̂  m





9. For the vectors A  3 î  4 ĵ  5 k̂ m , B  - 2 î  7 ĵ  3 k̂ N , and

A. Write - 4 C in polar form.


B. Find A  B
 
C. Find A  B

D. What is the angle between the vector A and the positive x-axis?
10. A 100 kg crate sits on the floor of a freight elevator that starts from rest on the ground
floor of a building at t = 0 s and rises to the top floor during an 8.0 s interval. The speed
of the elevator as a function of time is shown in the figure below:
12
v (m/s)
10
8
6
4
2
0
0
1
2
3
4
5
6
7
8
9 10
t (s)
A. What is the approximate height of the top floor of the building compared to the ground
floor?
B. What is the magnitude of the maximum force applied by the elevator on the crate
during the trip? (Hints: What do we normally call the force that a floor applies to an
object? How is the information in the graph related to forces?)