PROBLEM SET
Application of Newton’s Laws
(lifted from Chapter 4 of Physics: Principles with Applications 6th edition by Douglas Giancoli)
1. A coin is placed 11.0 cm from the axis of a rotating turntable of variable
speed. When the speed of the turntable is slowly increased, the coin remains
fixed on the turntable until a rate of 36 rpm* is reached and the coin slides
off. What is the coefficient of static friction between the coin and turntable?
2. A sports car of mass 950 kg (including driver) crosses the rounded top of a hill
(radius = 95 m) at 22 m/s. Determine the normal force exerted by the road on
the car.
3. How many revolutions per minute* would a 15-m diameter Ferris wheel need
to make for the passengers to feel “weightless” at the topmost point?
4. How fast (in rpm*) must a centrifuge rotate if a particle 9.00 cm from the axis
of rotation is to experience an acceleration of 115,000 g’s?
5. A flat puck (mass M) is rotated in a circle on a frictionless air-hockey tabletop,
and is held in this orbit by a light cord connected to a dangling block (mass m)
through a central hole as shown. Show that the speed of the puck is given by
mgR
v
M
*Note:
Recall how to translate angular velocity in rpm into tangential velocity in m/s:
where r is radius in meters and

v  r
is angular velocity in rpm
Perform dimensional analysis as follows to convert rpm into rad/s
 rev   2rad   1 min  
rpm  
 x
 x

 min   1rev   60s 
So tangential velocity is in m(rad/s) or m/s as rad is practically dimensionless.
Recall
that 1 radian is the angle subtended by an arc whose length is
equal to the radius. Since there are 2  r in one circumference, there are
also 2 radians in one revolution.