# Principles of Technology

## Mechanical Resistance (4:1)

### Review Worksheet

If you understand and can do these problems you should do well on the quiz.

1. What is the difference between "streamline" and "laminar" flow?

2. What is the formula for Drag Resistance?

3. Re-arrange the equation to solve for the other 2 variables.

4. What is the formula for calculating friction between 2 objects?

5. Re-arrange the equation to solve for the other 2 variables.

6. Transfer the equations into the following chart:

#### Drag ( ____ solids; ____ fluids )

7. A drag force of 15,000 lbs. is experienced by an airplane moving through the atmosphere at 250 miles per hour. What is the drag resistance on the airplane?

8. A "Putterboat" moving through the water at 30 meters per second experiences a drag resistance of 1725 newton/meter/second. How much force is propelling the boat through the water?

9. Keith jumps head first out of a hot air balloon. As he descends towards the ground he is moving with a force of 325 lbs. and is meeting with a drag resistance of 27.7 pound/feet/second. How fast is he going (and will he break the ground when he hits)?

10. A steel drum which weighs 347.6 pounds is sitting on a steel floor.

a. Calculate the force needed to get it moving.

b. Calculate the force needed to keep it moving.

c. Calculate the force needed to move it if metal rollers are placed between the drum and the floor.

11. A force of 1500 newtons will cause a stone sled (which weighs 2150 newtons) to begin sliding across a gymnasium floor made out of dinosaur skin.

a Calculate the coefficient of friction needed to get the sled moving.

b. Will it take more or less force to keep it moving once it gets started (remember that this species of dinosaur is now extinct).