SIMPLE MACHINES 207- Use sketches to show what is meant
by: (a) a first-order, (b) a second- order,
(c) a third-order lever system. Give one
practical use for each type of lever.
Exercise 95 Multi-choice questions on
simple machines (Answers on
page 285)A simple machine requires an effort of 250 N
moving through 10 m to raise a load of
1000 N through 2 m. Use this data to find the
correct answers to questions 1 to 3, selecting
these answers from:(a) 0.25 (b) 4 (c) 80% (d) 20%
(e) 100 (f) 5 (g) 100% (h) 0.2
(i) 25%- Find the force ratio.
- Find the movement ratio.
- Find the efficiency.
The law of a machine is of the formFe =
aFl+b. An effort of 12 N is required to raise
a load of 40 N and an effort of 6 N is required
to raise a load of 16 N. The movement ratio
of the machine is 5. Use this data to find the
correct answers to questions 4 to 6, selecting
these answers from:(a) 80% (b) 4 (c) 2.8
(d) 0.25 (e)
1
2. 8(f) 25%(g) 100% (h) 2 (i) 25%
- Determine the constant ‘a’.
- Find the limiting force ratio.
- Find the limiting efficiency.
- Which of the following statements is
false?
(a) A single-pulley system changes the
line of action of the force but does
not change the magnitude of the
force, when losses are neglected.(b) In a two-pulley system, the force
ratio is^12 when losses are neg-
lected.(c) In a two-pulley system, the move-
ment ratio is 2.(d) The efficiency of a two-pulley
system is 100% when losses are
neglected.- Which of the following statements con-
cerning a screw-jack is false?
(a) A screw-jack changes both the line
of action and the magnitude of the
force.(b) For a single-start thread, the dis-
tance moved in 5 revolutions of the
table is 5l,wherelis the lead of the
screw.(c) The distance moved by the effort is
2 πr,whereris the effective radius
of the effort.(d) The movement ratio is given by
2 πr
5 l- In a simple gear train, a follower has 50
teeth and the driver has 30 teeth. The
movement ratio is:
(a) 0.6 (b) 20 (c) 1.67 (d) 80- Which of the following statements is
true?
(a) An idler wheel between a driver
andafollowerisusedtomakethe
direction of the follower opposite
to that of the driver.(b) An idler wheel is used to change
the movement ratio.(c) An idler wheel is used to change
the force ratio.(d) An idler wheel is used to make the
direction of the follower the same
as that of the driver.- Which of the following statements is
false?
(a) In a first-order lever, the fulcrum is
between the load and the effort.(b) In a second-order lever, the load is
between the effort and the fulcrum.