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**Physics Mid-Term Exam revision 8/19/14**

**Directions:** It is important that you provide answers in your own words. Please focus only on information from the text/eBook to create your own solutions. Please do not use direct information from an outside source (especially copying and pasting from an “answer” website). Use of direct information from an outside source is against school policy. *All answers will be checked for plagiarism. **Instances of plagiarism* *can result in probation or possible dismissal from the school. *

**Grading:*** Please be sure to follow all guidelines (number of sentences/showing all calculations) and to provide the correct metric units of measure. All questions are 5 points (1 point for sentence number /correct units).*

- Makayla is talking to Mia about the whether we ever landed on the Moon. Mia says,” I have a theory about that.” Using 3 – 4 complete sentences, what is wrong with Mia’s use of the term “theory” in this instance?

- Choose
of the scenarios below, then design an experiment and describe a procedure to enable you to make an estimate of the*ONE**average speed*. Your description should include the materials you would need and how you would use them to collect the data you need. - A baseball thrown from outfield to home plate
- The wind
- A raindrop
- A hand moving back and forth as fast as possible
- The tip of a swinging baseball bat
- An eye blinking
- A whisker growing

- There are many familiar situations in which the net force on a body is zero and yet the body moves with a constant velocity. One example is described below:

*A car traveling at constant speed on a straight road has the force of the road on the tires just balanced by the force of air friction. If the gas pedal is depressed further, the tires will push against the road harder and the road will push against the tires harder; so the car will accelerate forward – until the air friction builds up enough to balance the greater drive force.*

* * Give another example of a body moving with constant velocity under balanced forces. Specify the cause of each force on the body and explain how these forces could be changed to affects the body’ motion.

- If a person weighs 500 N on Earth, what would she weigh on Jupiter, where the acceleration due to gravity is 26 m/s
^{2}? Show all work leading to your answer.

- If a freely falling rock were equipped with a speedometer, by how much would its speed readings increase with each second IF it were on a planet where
*g*= 20 m/s^{2}? Show all work leading to your answer.

- Cleo and Clare are looking from their balcony to a swimming pool below that is located 15 m horizontally from the bottom of their building. They estimate the balcony is 45 m high and wonder how fast they would have to jump horizontally to succeed in reaching the pool. What calculations would you show to help them determine the answer? Evaluate the practicality of their being able to succeed at jumping into the pool.

- An airplane has a gun that fires bullets straight ahead at the speed of 600 miles per hour when tested on the ground while the plane is stationary. The plane takes off and flies east at 600 miles per hour. Explain whether
*each*of the following is possible for the pilot to measure: - When fired directly ahead the bullets move eastward at a speed of 1200 miles per hour
- When fired in the opposite direction (by turning the gun westward, but not the plane), the bullets drop vertically downward
- If fired vertically downward (by turning the gun downward, but not the plane), the bullets move eastward at 600 miles per hour while they fall.

- A falling 50-kg skydiver experiences an upward acceleration of 6.2 m/s
^{2}when she opens her parachute. Show (by calculation) how much drag force is produced by the parachute.

- In three scenarios a truck is towing a boat on a trailer. Using 3 – 4 complete sentences indicate which scenario(s) (if any) is the force of the truck on the trailer greater than the force of the trailer on the truck:

Scenario A: mass_{truck} = 1000 kg, mass_{boat and trailer} = 500 kg; velocity = 20 m/s

Scenario B: mass_{truck} = 800 kg, mass_{boat and trailer} = 800 kg; velocity = 20 m/s

Scenario C: mass_{truck} = 500 kg, mass_{boat and trailer} = 1000 kg; velocity = 15 m/s

- A bug and the windshield of a fast-moving car collide. Indicate whether each of the following statements is True or False (1 point each)
- The forces of impact on the bug and on the car are the same magnitude.
- The impulses on the bug and non the car are the same magnitude
- The changes in speed of the bug and of the car are the same magnitude.
- The changes in momentum of the bug and of the car are the same magnitude.
- The accelerations of the bug and the car are the same magnitude.

- Betty and Bianca weigh the same amount and they climb a flight of stairs. Betty climbs the stairs in 30 seconds. Bianca climbs the stairs in 40 seconds. In terms of force, work and power, evaluate which of the three quantities (if any) is greater for Betty or for Bianca? Justify your answers using 3 – 4 complete sentences.

- Leon’s bicycle wheels have a circumference of 2 m. What is his linear speed when the wheels rotate at 1 revolution per second? Show all work leading to your answer.

- This graphic shows a scene from a trapeze act. Write 3 – 4 complete sentences to describe the physics pictured in this scene. Use the terms
*inertia*,*centripetal acceleration*,*force*,*gravity*, and*velocity*in your description.

- Using 6400 km as the radius of Earth, calculate how high above Earth’s surface you would have to be in order to weigh 1/16
^{th}of your current weight. Show all work leading to your answer OR describe your solution using 3 -4 complete sentences.

- The sun’s mass is about 2.7 x 10
^{7}times greater than the moon’s mass. The sun is about 400 times farther from Earth than the moon. How does the gravitational force exerted on Earth by the sun compare with the gravitational force exerted on Earth by the moon?

- At a particular point, a satellite in an elliptical orbit has a gravitational potential energy of 7000 MJ with respect to Earth’s surface and a kinetic energy of 4000 MJ. At another point in its orbit, the satellite’s potential energy is 2000 MJ. What is its kinetic energy at that point? Show all calculations leading to your answer.

- If a stationary cart is struck head-on by a cart with twice mass of the stationary one and a velocity of 5 m/s, what will be the new velocity of the stationary cart if the collision is
*inelastic*? Show all calculations leading to an answer.

- A 2.0-gram bullet is shot into a tree stump. It enters at a speed of 3.00 x 10
^{4}cm/s and comes to rest after having penetrated 0.05 m in to the stump. What was the average force during the impact? Show all calculations leading to an answer.

- Can you get younger by traveling at speeds near the speed of light? Explain using 3 or more complete sentences.

- A beam of light and a baseball are both affected by gravity. Why is the path of the baseball very different than the path of the light beam? Use 3 – 4 complete sentences in your explanation.