2—6.
If the handle of a jackscrew is
turned 16 complete revolutions to
raise the jack 2 inches, the pitch
of the screw is
1.
1/32 in
2.
1/16 in
3.
1/8 in
4.
1/4 in
2–7.
You are pulling a 21–inch lever to
turn a jackscrew having a pitch of
3/16 inch.
The theoretical
mechanical advantage of the
jackscrew is about
1.
1,000
2.
700
3.
400
4.
100
2–8.
A jackscrew has a handle 35 inches
long and a pitch of 7/32 inch. If
a pull of 15 pounds is required at
the end of the handle to lift a
3,000–pound load, the force
expended in overcoming friction is
1.
12 lb
2.
9 lb
3.
3 lb
4.
5 lb
2-9.
Refer to textbook figure 5–3.
How
many complete turns of the thimble
are required to increase the
opening of the micrometer by 1/4
inch?
1.
25
2.
10
3.
5
4.
4
When answering items 2–10 and 2–11,
o
refer to textbook figure 5–4.
2–10.
If the micrometer’s thimble is
turned exactly five complete
revolutions,
the new reading is
2–11.
Assume that the graduation mark 5
on the thimble is opposite point X.
How much farther do you open the
micrometer in turning the thimble
until the graduation mark 15 is
opposite the point for the first
time?
1.
0.125 in
2.
0.010 in
3.
0.0125 in
4.
0.0010 in
2–12.
How do you find the actual
mechanical advantage that a
jackscrew provides in lifting a
load?
1.
Multiply the length of the jack
handle by the radius of the
screw and then divide by the
pitch of the screw
2.
Divide the load by the amount
of effort required to lift the
load
3.
Multiply the length of the jack
handle by 2 and then divide by
the pitch of the screw
4.
Divide the distance the screw
travels by the number of turns
it makes and then subtract the
amount of frictional resistance
2–13.
If a jackscrew has a pitch of 5/32
inch, the length of the handle
required to obtain a theoretical
mechanical advantage of 800 is
about
1.
30 in
2.
25 in
3.
20 in
4.
15 in
2–14.
If a jackscrew requires a force of
15 pounds at the end of the handle
to lift a 3,000 pound load, its
actual mechanical advantage is
1.
4,500
2.
2,000
3.
450
4.
200
1.
0.753 in
2.
0.703 in
3.
0.628 in
4.
0.517 in
13
