Machine Practice (use your worksheet)

Connect the efficiency with the pulley to belongs to.

a

b

c

87.5%

86.25%

82.5%

What is the mechanical advantage of each can opener?

• Type 2

• 14

• Type 1

• 12

• Type 3

• 13

The mechanical advantage of this inclined plane is...(MA=Resistance Force/Effort Force)

• 2.4

• 3.4

• 4.4

A box of weight W is lifted by a force F using a lever as shown below.

What is the mechanical advantage of the lever (MA=Input Distance/Output Distance)?

• 0.5

• 2

• 3

• 6

If there is 100N hanging from the system, what force does each rope support?

j

h

f

d

b

100J

300J

12m

4

200J

5

15m

20N

25N

450J

Answer explanation

There are 5 supported ropes.

To lift 3m, there needs to be 15m rope (5 ropes * 3m each)

Each ropes supports 20N of 100N of Force.

Your work is W=F*d -> 20N * 15m (you pull enough for all 5 ropes to raise 3m each) 300J

At 50% efficient, you have to do the extra 50% of work (150J). So 300J + 150J = 450J

Or 300J * 1.5 = 450J

Use the given information to identify the answers about this pulley system.

j

h

f

d

b

5

3744J

3120J

2496J

4

24m

2995J

30m

104N

130N

Answer explanation

There are 5 supported ropes.

To lift 6m, there needs to be 30m rope (5 ropes * 6m each)

Each ropes supports 104N of 520N of Force.

Your work is W=F*d -> 104N * 30m (you pull enough for all 5 ropes to raise 6m each) 3120J

At 80% efficient, you have to do the extra 20% of work. So 3120J * 1.20 = 3744J

Jeff is a landscaping contractor and lifts a rock weighing 600 pounds by wedging a board under the rock. Jeff weighs 150 pounds and puts all of his weight on the lever. How much mechanical advantage did the lever provide to Jeff in lifting the rock?

[MA = Resistance Force / Effort Force] (a)  

• 4
• 0
• 2
• 8

What is the mechanical advantage of a lever if you lift a 300N boulder and you only push down with 50 N?

MA = Resistance Force / Effort Force (a)  

• 6
• 250
• 50
• 60

Complete each fact about this pulley system.

j

h

f

d

b

50J

16.7N

500J

2

20m

30m

25N

625J

3

300J

Answer explanation

There are 2 supported ropes.

To lift 10m, there needs to be 20m rope (2 ropes * 10m each)

Each ropes supports 25N of 50N of Force.

Your work is W=F*d -> 25N * 20m (you pull enough for all 2 ropes to raise 10m each) 500J

At 75% efficient, you have to do the extra 25% of work. So 500J * 1.25 = 625J

Complete each fact about this pulley system.

j

h

f

d

b

5

50N

20m

1375J

1100J

25m

1000J

62.5N

1250J

4

Answer explanation

There are 4 supported ropes.

To lift 5m, there needs to be 20m rope (4 ropes * 5m each)

Each ropes supports 62.5N of 250N of Force.

Your work is W=F*d -> 62.5N * 20m (you pull enough for all 4 ropes to raise 5m each) 1250J

At 90% efficient, you have to do the extra 10% of work. So 1250J * 1.10 = 1375J