a=~eT =. - Sharkey Physics

Bronco skydives and parachutes from a stationary helicopter. Various stages offall are
shown in positions a through!
Using
Newton's 2nd law,
a=~eT
=. W-I<
Wl
(VI
find Bronco's acceleration at each position
(answer in the blanks to the right). You need to
know that Bronco's rnass m is 100 kg so his
weight is a constant 1000N. Air resistance R
varies with speed and cross-sectional area as
shown.
.
Circle the correct answers.
a=
b
W -= 1000 N
N
~=IOOO
(3=
c
1. When Bronco's speed is least, his
acceleration is
2.
In which position(s) does Bronco
experience a downward acceleration?
(a) (b) (c) (d) (e) (f)
3. In which position(s) does Bronco
experience an upward acceleration?
w= /000
a=
_
a=
_
N
(a) (b) (c) (d) (e) (f)
4. When Bronco experiences an upward
acceleration, his velocity is
(still downward)
5. In which position(s)
velocity constant?
(upward also).
is Bronco's
(a) (b) (c) (d) (e) (f)
.~
~
6. In which position(s) does Bronco
experience terminal velocity?
(a) (b) (c) (d) (e) (f)
R--=IOOO
7. In which position(s)
greatest?
(a)
8.
(b)
(e)
(d)
N
is terminal velocity
(e)
(fJ
a= ------
If Bronco were heavier, his tem1inal
velocity would be
(greater)
(less)
(the same).
W:: /ODD N
1. Three boxes are piled up. Free-body diagrams
for each are shown.
a. What is the weight of each box?
b. Which two forces are equal from Newton's 3rd
law of equal and opposite forces and the contact
between the top two boxes?
c. Which two forces are equal from Newton's 3rd
law and the contact between the bottom two
boxes?
D
D
L1J
'4=8N
D
Lf
2. Three masses are hung by strings. A free-body
diagram for the center block is shown; there is one
upward force and two downward forces as labeled.
a. Draw a free-body diagram for the upper block
and for the lower block; label the forces.
b. One of the forces on the upper block is equal
and opposite to one of the forces on the middle
block. Which two forces are equal and
opposite?
c. One of the forces on the middle block is equal
and opposite to one of the forces on the lower
block. Which two forces are equal and
opposite?
3. Three books are stacked on the table. A free
body diagram for the lowest book is shown.
a. Draw free-body diagrams for the upper and
middle book.
b. Identify an equal-and-opposite pair of forces
between the upper and middle books.
c. Identify an equal-and-opposite pair of forces
between the middle and lower books.
d. Of all the forces in these diagrams, which force
is the biggest?
e. Of all the forces in these diagrams, identify the
smallest force. This is a tie; which forces are
tied for smallest?
/
/ - - -~nsi0'2
,
T2

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