Environmental Engineering Reference
In-Depth Information
where
t
is measured in seconds and the magnitude of
s
is measured in km.
(a) What is the speed of the missile at
t
=
0? In which plane is the velocity
at this time?
(b) What is the speed of the missile at
t
30 s? What is the angle between
the velocity vector and the (positive)
z
axis at this time?
1.9 An airport travelator of length 50.0 m moves at a speed of 1.0 ms
−
1
.An
athlete capable of running at a speed of 10.0 ms
−
1
bets a friend that he can
run to the end of the travelator and back again in exactly 10.0 s, as long as
the time to change direction and restart is not included. The athlete loses the
bet. What mistake has the athlete made? (Assume that at the start of each leg,
the athlete is already running at full speed.)
1.10 A ferryman crosses a fast-flowing river. The ferryman knows that her boat
travels at a speed
v
in still water, and that with the engine off the boat will
driftataspeed
u
in a direction parallel to the bank, where
u
is less than
v
.
If the line joining the two ferry stations makes a right-angle with the bank,
and the stations are separated by a distance
d
, derive an expression for the
time taken to cross the river. What happens if
u
is greater than
v
?
=
