Notes
Reminders:
• HW due Wednesday
• “Standard” Help Sessions and Office Hours continue
• Exam re-grades due Friday
– Please write a short note explaining what you think
was graded incorrectly
You speed down a road in your new roadster, approaching a
cylindrical bump which has a radius of curvature of 50 m. How
fast do you have to be going such that your tires lose contact with
the road at the top of the bump?
R = 50 m
A puck moves in a circle of radius r0 with a constant speed v0 on
a level, frictionless table. A string is attached to the puck, passes
through a frictionless hole, and is attached to a hanging object of
mass M.
v0
r0
M
The puck is now made to move with a speed v´=2v0, with the
mass M left unchanged. The new acceleration a´ of the puck and
radius r´ of the circle are now given by:
(B) a´=2a0 and r´ = r0
(A) a´= 4a0 and r´ = r0
(C) a´= 2a0 and r´ = 2r0
(D) a´= a0 and r´ = 4r0
v0
r0
M
The puck continues to move in a circle with a speed v´=2v0, but
now the mass M is increased to 2M. The new acceleration a´ of
the puck and radius r´ of the circle are now given by:
(A) a´= 4a0 and r´ = r0
(B) a´=2a0 and r´ = r0
(C) a´= 2a0 and r´ = 2r0
(D) a´= a0 and r´ = 4r0
(Here a0 and r0 are the original acceleration and radius.)
You are traveling with velocity v0 in a car of mass M,
heading directly for a brick wall a distance D away.
Should you swerve or hit the brakes? Calculate:
a) The minimum linear distance in which you can stop
by slamming on the brakes.
b) The minimum radius of a circular path that you
would take by swerving hard.
In both cases, assume that there is no skidding, and that
you are given the coefficient of static friction s.
A 100g block sits on a horizontally rotating turntable. The
turntable makes one revolution per second. The block is located
10 cm from the axis of rotation of the turntable.
a) Draw a free body diagram for the block.
b) What is the frictional force acting on the block?
c) The block will slide off the turntable if it is placed at a radius
larger than 16 cm. What is the coefficient of static friction
between the block and the turntable?