Question

Using Science Skills
Use the diagram to answer each question. Write
the answers on a separate sheet of paper.
Figure 14 - 2, A picture of machine a holding machine b halfway
1. Applying Concepts Look at Figure 14-2.
If Machine A moves through an input
distance of 4.0 m, what is the output
distance of Machine B?
2. Classifying What type of simple machine
is Machine A in Figure 14-2?
3. Interpreting Graphics What is the IMA
of Machine B in Figure 14-2?
4. Interpreting Graphics As shown in
Figure 14-2, Machines A and B operate
together as what type of machine?
5. Comparing and Contrasting In Figure
14-2, how does the work input of
Machine B compare with the work
output of Machine A?
Problem
Write the answers to each question on a separate sheet of paper.
1. A worker uses a cart to move a load of bricks weighing 680 N a
distance of 10 m across a parking lot. If he pushes the cart with a
constant force of 220 N, what amount of work does he do? Show
your work.
2. A girl lifts a 100-N load a height of 2.0 m in a time of 0.5 s. What
power does the girl produce? Show your work.
3. The input force of a pulley system must move 6.0 m to lift a 3000-
N engine a distance of 0.50 m. What is the IMA of the system?
Show your work.
4. A 16-N force applied to the handle of a door produces a 30-N
output force. What is the AMA of the handle? Show your work.
5. A force of 12 N is applied to the handle of a screwdriver being
used to pry off the lid of a paint can. As the force moves through a
distance 0.3 m, the screwdriver does 32 J of work on the lid. What
is the efficiency of the screwdriver? Show your work.

Answer 1

Using Science Skills (Figure 14-2)
1. Output distance of Machine B = 2.0 m. (If A moves 4.0 m and B is moved half as far, output = 4.0/2 = 2.0 m.)
2. Machine A is a pulley.
3. IMA of Machine B = 2. (IMA = input distance / output distance = 4.0 m / 2.0 m = 2.)
4. Machines A and B operate together as a compound machine (a compound pulley system).
5. The work input to Machine B equals the work output of Machine A (neglecting friction/losses).

Problems
1. Work = F · d = 220 N · 10 m = 2200 J.

2. Work = F · d = 100 N · 2.0 m = 200 J.
Power = work / time = 200 J / 0.5 s = 400 W.

3. IMA = input distance / output distance = 6.0 m / 0.50 m = 12.

4. AMA = output force / input force = 30 N / 16 N = 1.875 ≈ 1.88.

5. Input work = F · d = 12 N · 0.3 m = 3.6 J.
Efficiency = (work output / work input) · 100% = (32 J / 3.6 J) · 100% ≈ 888.9% ≈ 8.89 × 10^2 %.
Note: An efficiency >100% is not physically possible for an isolated simple machine; this indicates inconsistent data (an additional energy source or a typo in the problem).