## GBS Physics Resources

The Physics Classroom

# Henderson's Physics 163

### Chapter 10 Opening Questions

Wednesday, December 12:

Identify the following scenarios as being either examples or a non-examples of work. For each which are non-examples, explain why it is not an example of work.

1. A teacher pushes against a wall for 5 minutes and becomes exhausted.

2. A group of teenagers push upon a car to move it out of a ditch during a snowstorm.

3. Superman pushes upon truck to prevent it from rolling down a hill.

Thursday, December 13:

The work done on an object is calculated using the equation:
Work = F • d •dosine (theta)

For each of the following situations, identify the value of theta in the work equation.

1. A 12-N force is applied to a cart in a direction parallel to the inclined plane in order to move the cart from the floor 2.0 meters along the incline to the top of a lab bench. The incline makes an angle of 30-degrees with the horizontal.

2. A student exerts a 39.2-N uopward force on a 4.0-kg suitcase as he walks a distance of 80-meters along a horizontal walkway at an airport.

3. Fido has the hots for Fidella. So when Mr. Jones takes a Fido for a walk around the block, he must be careful to restrain Fido when walking by Fidella's house. One day, Mr. Jones pulls upward and rightward at an angle of 30 degrees with the horizontal to pull Fido rightwards a distance of 1.2 meters.

4. A leftward friction force of 8200 N acts upon a 920-kg rightward moving car as it skids to a stop over a distance of 26.0 meters.

Friday, December 14:

Two physics students, Will N. Andable and Ben Pumpiniron, are in the weightlifting room. Will lifts the 100-pound barbell over his head 10 times in one minute; Ben lifts the same100-pound barbell over his head 10 times in 10 seconds.
Which student does the most work? ______________

Which student delivers the most power? ______________

Tuesday, December 18:

True or False:
A machine is a device used to transfer energy to a system. A machine makes a manual task easier by making the amount of work needed to complete the task less than what it would be if the task was done without the help of the machine.