22
1 Kinematics and Statics
or
a 1 = −
F
m
+ g
(1)
For downward motion, the equation of motion is
ma 2 = mg − F
or
a 2 = g −
F
m
(2)
For ascent
v 1 = 0 = u + a 1 t = u −
F
m
+ g
t 1
t 1 =
u
g +
F
m
(3)
v 1
2
= 0 = u
2
+ 2a 1 h
u =
2h
g +
F
m
(4)
where we have used (1). Using (4) in (3)
t 1 =
2h
g +
F
m
(5)
For descent v 2 = 2a 2 h
v =
2h
g −
F
m
(6)
where we have used (2)
t 2 =
v
a 2
=
2h
g −
F
m
,
(7)
where we have used (2) and (6)
From (5) and (7)
t 2
t 1
=
g +
F
m
g −
F
m
(8)