Physics 201 MWF10:20 Fall 1997 (Ford)
Exam I Chapts. 1-5 in SZY College Physics
Show all your work. Partial credit will be given if earned. Write your
answers in the blanks provided.
(16 pts) 1. An airplane travels due north relative to the earth. A wind of
12.0 m/s blows due west. The airspeed of the plane (the speed
of the plane relative to the air) is 30.0 m/s.
a) How much time does it take the plane to reach a point 8000 m due north of
its starting point?
Ans. ___291 s___
b) In what direction should the plane head? (That is, what is the direction
of the velocity of the plane relative to the air?)
Ans.___23.6° E of N___
(20 pts) 2. A small rock is thrown horizontally from the roof of a building
that has height H above ground. The rock strikes the ground a horizontal
distance of 50.0 m from the base of the building, 2.0 s after it was thrown.
a) What was the initial velocity v0 of the rock?
Ans. ___25 m/s___
b) What is the height H of the building?
Ans. ___19.6 m___
(20 pts) 3. The engineer of a passenger train traveling at 25 m/s
sights a freight train whose caboose is 170 m ahead on the same track. The
freight train is traveling in the same direction as the passenger train with
a speed of 15.0 m/s. The engineer of the passenger train
immediately applies the brakes, causing a constant acceleration of
-0.10 m/s2 while the freight train continues with constant
speed.
a) How long after the brakes are applied will the trains collide?
Ans. ___18.8 s___
b) How fast will the passenger train be traveling just before it hits the rear
of the freight train?
Ans. ___23.1 m/s___
(22 pts) 4. A 3.0 kg box is placed on an incline that slopes upward at
37° above the horizontal. The coefficient of kinetic friction
between the box and the incline is 0.30. A horizontal force
F = 60 N pushes the box up the incline. (Note that F is
horizontal and not parallel to the incline.)
a) What is the magnitude of the normal force that the incline surface
exerts on the box?
Ans. ___59.5 N___
b) What is the acceleration of the box?
Ans. ___4.2 m/s___
(22 pts) 5. A block of mass 5.0 kg is on a frictionless incline of angle
37°. It is connected by a massless rope that passes over a
massless, frictionless pulley to a hanging block of mass m. When the
blocks are released from rest the 5.0 kg block slides down the incline with
an acceleration of 3.0 m/s2.
a) While the blocks are moving, what is the tension in the rope?
Ans. ___14.4 N___
b) What is the mass m of the hanging block?
Ans. ___1.12 kg___