MCAS Physics Exams MCAS 2019 Session 2

Open-Response Questions
• BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION.
• If you do the work in your head, explain in writing how you did the work.

Refer to the following information for the next three questions.

Inflatable launchers are large, air-filled bags that float on the surface of the water at lakes, water parks, and community pools. A launcher works by transferring energy from one person to another. A person sitting on a launcher is launched into the air when another person jumps onto the bag. The diagram shows a boy and a girl using an inflatable launcher at a lake.

The 75 kg girl is standing on a platform 15 m above the top of the launcher.
 a. Calculate the gravitational potential energy of the girl relative to the top of the launcher. Show your calculations and include units in your answer.

 The girl steps off the platform and lands on the launcher. b. Describe how the girl’s kinetic energy and gravitational potential energy change during the time interval that begins when she steps off the platform and ends just before she lands on the launcher.

 The boy is launched several meters into the air but wants to be launched higher. c. Describe one change that could be made so that the boy would be launched higher. Explain your reasoning.

Refer to the following information for the next four questions.

A student heated 235 g of water in a beaker until the water reached 100°C. The student removed the beaker from the heat and placed the beaker on a counter in a 23°C room. The student recorded the temperature of the water every 4 minutes for 20 minutes. The data are shown in the table.

 a. Did heat flow from the air to the water or from the water to the air? Include data from the table to support your answer.

 b. Identify the average temperature of the air in the room at 20 min.

 c. Were the water and the air in thermal equilibrium at 20 min? Explain your answer.

 The specific heat of water is 4.19 J/g°C   d. Calculate the change in thermal energy of the water from 0 min to 20 min. Show your calculations and include units in your answer.

Refer to the following information for the next four questions.

 Circuit X has the same total resistance as circuit W, but circuit X has only one resistor, R4.   a. Calculate the resistance of R4. Show your calculations and include units in your answer.