Multiple Choice Items:

1. A small airplane heads west from an airport at 120 kilometers per hour. It is flying into a wind blowing from the west at 20 kilometers per hour. After an hour, how far will the airplane be from the airport?

A. 120 kilometers

B. 140 kilometers

C. 80 kilometers

D. 100 kilometers

2. An advertising blimp and a small airplane weigh about the same. The blimp’s nose is 9 meters wide. The airplane’s nose is 1.5 meters wide. The blimp has one landing wheel. The airplane has three landing wheels. Both taxi down the runway at 20 kilometers per hour and then cut their engines. The blimp stops before the airplane. Why is that?

A. The blimp has fewer wheels.

B. The blimp has more drag.

C. The airplane is heavier than air.

D. The airplane flies faster.

3. Two furniture movers are not strong enough to lift a table into the back of a truck. However, they can easily carry the table up a ramp into the truck. What mechanical advantage does the ramp give the movers?

A. They exert less force over a longer distance.

B. They exert less force over a shorter distance.

C. They exert more force over a longer distance.

D. They exert more force over a shorter distance.

4. A sailboat is moving across a lake. Forces acting on it include gravity, friction with the water, wind gusts, and air resistance. Which force is unbalanced?

A. Gravity

B. Air resistance

C. Wind gusts

D. Friction with water

5. Movers must exert 100 kilograms of force to lift a particular box 3 meters onto a loading dock. If they slid it up a ramp that was 15 meters long, how much force would they have to exert?

A. 20 kilograms

B. 100 kilograms

C. 15 kilograms

D. 120 kilograms

Multiple Choice Answer Key:

Short-Answer Items:

6. A warehouse uses a pulley to raise boxes to a second floor loft. They replace the pulley with a block-and-tackle with a mechanical advantage of 2. They find that they can replace the two-horsepower electrical motor they had used for the pulley with a one-horsepower motor. But at the end of the month (having moved the same number of boxes as they did in the previous month) they find they are using the same amount of electricity as they did with the larger motor. Why?

Short-Answer Key and Scoring Rubrics:

6. The warehouse uses the same amount of electricity as before because mechanical advantage means you can apply less force over a larger distance to complete a task, but the amount of energy consumed for the task remains the same.

Performance Assessment:

An architect is given the task of designing a connection between two halves of a warehouse, one of which is four feet higher than the other. Steel drums weighing 400 pounds are stored on both sides of the warehouse. The warehouse manager wants to ensure that, if the front-end loader broke down, one person could move a drum from one end to the other by rolling it or wheeling it on a handcart. That way the warehouse would need only one person on call at any one time. If one person could not move a drum, hiring additional workers would cost the warehouse at least $35,000 yearly for each additional worker. But if constructing the connection between the two halves of the warehouse costs more than hiring additional workers, then the manager is willing to hire additional people instead of undergoing the construction project.

The architect identifies three possible solutions:

A. A metal stairway replacing an existing wooden one, with four steps, each one foot high. The workers could use a handcart to move a drum up the stairs one step at a time, with each step representing a vertical lift of one foot. Building the stairs would cost $1,500.

B. A ramp paralleling the wooden stairway. Available space allows for a ramp up to 16 feet long. Drums could be rolled up the ramp. Building this ramp would cost $5,000.

C. A ramp perpendicular to the stairs running nearly the width of the warehouse, or 40 feet. Drums could be rolled up the incline. Building this ramp would cost $25,000.

The architect also determines that a hard-working person can be expected to regularly exert a force of 50 pounds.

1. Remembering that work equals force times distance, determine the force needed to move a 400-pound drum up A, B, and C. In the case of A, only one step needs to be accounted for since the workers can rest between steps; the total work will be 400 pounds. With B and C the total work will be 400 pounds times four feet.

2. What advice should the architect give to the warehouse manager?

Performance Assessment Scoring Rubric: