Download Physics 111 HW6 - University of St. Thomas

Physics 111 HW5
assigned 14 February 2011
RV-03. (Young & Friedman 11th ed. Ex. 3.36) A railroad flatcar is traveling to the right at a
speed of 13.0 m/s relative to an observer standing on the ground. Someone is riding a motor
scooter on the flatcar. What is the velocity of the motor scooter relative to the flatcar if it
velocity relative to the observer is
a) 18.0 m/s to the right?
b) 3 m/s to the left?
c) 0 m/s?
RV-04. (Young & Friedman 11th ed. Ex. 3.40) An airplane pilot wishes to fly due west. A wind
of 80.0 km/h is blowing toward the south. The airspeed of the plane (its speed in still air) is
320.0 km/h. Use a vector diagram to help you answer the following.
a) What direction should the pilot head?
b) What is the speed of the plane over the ground?
RV-05. (Young & Friedman 11th ed. Prob. 3.85) In a World Cup soccer match, Juan is running
due north toward the goal with a speed of 8.00 m/s relative to the ground. A teammate kicks
the ball in such a way that it travels at a speed of 12.0 m/s moving in a direction 37.0 o E of N
relative to the ground. What are the magnitude and direction of the ball’s velocity relative to
Juan?
CenA-01. (Young & Friedman 11th ed. Ex. 3.29) The Earth has a radius of 6380 km and turns
around once on its axis in 24 hours.
a) What is the radial acceleration of an object at the Earth’s equator? Give your answer in
m/s2 and in terms of g.
b) If the radial acceleration at the equator is greater than g, objects will fly off the Earth’s
surface and into space. What would the period of the Earth’s rotation have to be for this
to occur?
CenA-02. (Young & Friedman 11th ed. Ex. 3.33-4) A Ferris
wheel with radius 14m is turning about a horizontal axis
through its center. The linear speed of a passenger on the
rim is constant and equal to 7.00 m/s. What are the
magnitude and direction of the passenger’s acceleration as
she passes through
a) the lowest point in her circular motion?
b) the highest point in her circular motion?
c) How long does it take the Ferris wheel to make one
revolution?
Now the same Ferris wheel is at rest, and just starts up. At a
given instant, a passenger on the rim of the wheel is passing
through the lowest point of her circular motion, is moving at 3.00 m/s, and is gaining speed at
a rate of 0.500 m/s2.
d) Find the magnitude and direction of the passenger’s acceleration at this instant.
(over)
CenA-03. You start at rest at point A and travel in the path shown at right
with a constant linear/tangential acceleration of 0.4 m/s2 to point B.
What is
a) your average velocity for the A → B trip?
b) your average acceleration for the A → B trip?
c) your net instantaneous acceleration at point P, halfway around the
circular part?
A
10m
10m
B
GenFMA-01. A block of ice with mass m sits at rest on a friction-free, frozen lake. A constant
force F then acts on the block for a specific time T, resulting in the block having a speed v.
a) Start the block at rest again. If the force on and mass of the block are unchanged, but the
time the force acts on the block (T) is doubled, what is the new speed (in terms of v)?
b) Start the block at rest again. Now the force and time are unchanged from the first trip, but
the mass of the block is doubled. What is the speed of the block now (in terms of v)?
c) Start the block at rest again. Now the force is doubled, with the mass and time unchanged.
What is the speed of the block again?
d) Now repeat the trip again, only suppose that the force, time, and mass are all the same.
The only thing different now is that the force of gravity is somehow doubled. What is the
speed of the block again?
GenFMA-02. A dockworker applies a constant horizontal force of 80.0 N to a block of ice on a
smooth horizontal floor. The frictional force is negligible. The block starts from rest and
moves 11.0 m in 5.00 s.
a) What is the mass of the block of ice?
b) If the worker stops pushing at the end of 5.00 s, how far does the block move in the next
5.00 s?
GenFMA-03. (Young & Friedman 11th ed. Ex. 4.11) A hockey puck with mass 0.160 kg is at
rest at x = 0 on a frictionless, horizontal hockey rink. At time t = 0, a player applies a force
of 0.250 N to the puck, parallel to the x-axis; he continues to apply this force until t = 2.00s.
a) What are the position and speed of the puck at t = 2.00 s?
b) If the same force is again applied at t = 5.00s for another 2 seconds, what are the position
and speed of the puck at t = 7.00s?
(over)
P