>
k
m
=
r(t) = Bet + Cet , where
=
k
m
=
r(t) = Dt + E.
2
k
,
m
(285)
In view of these three cases, the special value of is k/m. Basically, if > k/m,
then in the rotating frame the centrifugal force (see Chapter 10) wins out over the
HW7 Solutions
sprin
in a
m
2.20. Block under an overhang
Lets break up the forces into components parallel and perpendicular to the over
hang. Let positive F; point up along the overhang. Balancing the forces parallel
and perpendicular to the overhang gives, respectively,
3.46. Equal tilts
18
CHAPTER 3. USING F = M A
The coordinates of the projectile are y = (v0 sin )t gt2 /2 and x = (v0 cos )t. The
projectile hits the plane when y/x = tan . Using the expressions for x and y , this
3.37. bv 2 force
gives t = 4v0 sin /g . T