 MCAS Physics Exams MCAS 2015 Session 2 Frozen food is submerged in a small insulated container of 95°C water. Which statement best describes the temperature of the food after two hours, assuming no heat is lost outside of the insulated container? A free-body diagram is shown below. What is the magnitude of the net force acting on this object? The graph below shows the relationship of voltage versus current for a circuit. This graph represents the relationship described by which of the following laws? The diagram below shows a planet moving in a circular orbit around a star. Four arrows are labeled W, X, Y, and Z. Which arrow represents the direction of the force that keeps the planet in its orbit? When astronauts landed on the Moon, radio signals helped them communicate with people on Earth. It took 1.3 s for a signal to travel from the Moon to Earth. Which of the following is the best estimate of the distance between Earth and the Moon? A seismic wave called a P-wave travels through the solid part of Earth. In a P-wave, the solid particles of Earth move parallel to the direction the P-wave travels. P-waves are which of the following types of waves? A 0.5 kg sphere is placed on top of a coiled spring. The coiled spring has 30 J of elastic potential energy. When  the spring is released, the sphere moves upward, as shown in the diagram below. Neglecting friction and the mass of the spring, what is the change in height (D h) of the sphere? A student heats 200 g of water from 20°C to 70°C. How much heat did the student add to the water if the specific heat for water is 4.2 J/g • °C? Which of the following is an example of simple harmonic motion? A planet with a radius equal to that of Earth has twice the mass of Earth. If an object weighs 800 N on Earth’s surface, how much will it weigh on the other planet? In which of the following situations will the observer perceive the highest frequency from the fire truck siren? Which of the following statements describes electromagnetic waves? The graph below represents a car’s motion as it accelerates from rest. Which of the following graphs best represents the relationship between the accelerating car’s position and time? At a given temperature, a longitudinal mechanical wave will travel fastest through which of the following? Food can be sterilized by exposing it to high-frequency radiation. The higher the frequency of electromagnetic radiation used, the better it can penetrate thick layers of food. Which part of the electromagnetic spectrum would be most effective for sterilizing food? The diagram below represents a light ray striking the surface of a flat, shiny object. What most likely happens to the light ray as it strikes the object’s surface? Two boxes with the same mass are placed on different shelves, as shown below. Which of the following statements compares the amounts of work required to lift the boxes from the floor onto the different shelves? Which of the following statements describes a difference between kinetic friction and static friction? Which of the following is a purpose of a battery in a circuit?

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 four questions. The diagram below shows three points on a roller coaster track. A car starts from rest at point X and travels along the track. Assume friction is negligible. a. Identify whether the car’s gravitational potential energy increases, decreases, or stays the same as the car moves from point X to point Y.

 b. Identify whether the car’s kinetic energy increases, decreases, or stays the same as the car moves from point Y to point Z.

 The car has a mass of 600 kg. c. Calculate the gravitational potential energy of the car at its maximum height. Show your calculations and include units in your answer.

 d. Calculate the maximum kinetic energy of the car. Show your calculations and include units in your answer.

Refer to the following information for the next four questions. A student was investigating cooling times for two pots made of different materials. One pot was stainless steel and the other pot was iron. The pots were placed on a table in a 25°C room. The pots were roughly the same size and shape, and contained the same amount of water. The pots and water were originally at 100°C. The student recorded the temperature of the water in each pot over time. The graph below shows the results. a. Determine the amount of time it took the water in the iron pot to cool from 100°C to 60°C.

 b. Based on the graph, which pot, the iron pot or the stainless steel pot, was a better conductor of thermal energy? Explain your answer.

 c. Identify two methods of heat transfer that occurred as the water in the pots cooled, and describe how the transfer of heat occurred for each method.

 d. Describe when the pots no longer experienced a net loss of thermal energy.

Refer to the following information for the next four questions. A floating object moves up and down 15 times in 60 s because of ocean waves.

 a. Calculate the period of the ocean waves. Show your calculations and include units in your answer.

 b. Calculate the frequency of the ocean waves. Show your calculations and include units in your answer.

 An additional wave property must be known in order to calculate the velocity of the ocean waves. c. Identify this additional wave property and draw a wave diagram showing how the property can be measured.

 d. Describe what will happen to the object if the amplitude of the ocean waves increases and all other wave characteristics stay the same.