# MASS Mechanical Concepts

#### Daryl is using a pulley system to lift a 100-pound box, but the pulleys are only 50% efficient. How many pounds of force is he using to move the box?

Correct!
Wrong!

Power Output divided by Efficiency = PO/E 100/.5 = 200lbs

#### An engine produces 90hp and is 90% efficient. So, how much horsepower is being lost due to inefficiency?

Correct!
Wrong!

The engine's total efficiency would be 90hp/.90 = 100hp. But the question is how much money is being lost due to engine inefficiencies. So we deduct the 90hp output from the 100hp output, which would be 100% efficient, and get 10hp. Inefficiency results in a loss of 10hp.

#### How much work did a rock climber put in if he used 660 newtons to climb a 30 meter cliff?

Correct!
Wrong!

660N is multiplied by 30m.

#### Mark must pull a truck for 1 minute. The truck weighs 115.5 tons. What is the bare minimum in terms of horsepower?

Correct!
Wrong!

To get the answer in pounds, multiply 115.5 by 2,000 (231,000 lbs). Next, divide that by the number of pounds a single horsepower can move every minute, which is 33,000.

#### The force required to move 550 pounds one foot in one second is usually referred to as:

Correct!
Wrong!

#### A pipe connects two identical covered liquid containers. How much force will the connecting pipe apply if one side receives 12 lbs of force?

Correct!
Wrong!

12 lbs. Because the containers are of same size and are pressured, the weight will be distributed uniformly.

#### 5,968 watts are needed by an elevator motor to drive the elevator. How many horsepower does the elevator's electric motor have?

Correct!
Wrong!

The solution is 5,968 watts divided by 746 watts.