Students are investigating the relationship between human population density and biodiversity. The amount of forest cover was used as a measure of the biodiversity of an area. The students averaged human population density and forest cover from locations with a range of population densities. The graph shows the students' results.

The students identified four resource management strategies intended to help preserve forest cover and maintain biodiversity.

The students then ran computer simulations to graphically compare the different resource management strategies.

Which graph shows results for a resource management strategy that will BEST preserve forest cover as population density increases?

Laser light of wavelength 785 nm in air travels from air (index of refraction = 1) into a glass block (index of refraction = 1.5).  The frequency of the light does not change when the light enters the glass.  How does the wavelength of the light change, if at all, when the light enters the glass, and what reasoning supports this claim?

A student performs an experiment in which a cart is pulled across a table by exerting a net force of 0.05 N on the cart.  Different amounts of mass are added to the cart for each trial.  The graph shows data from the experiment.

Based on the results from the experiment, what claim can the student make about the relationship between net force, acceleration, and mass?

Students are discussing a model of a system that consists of two parallel conducting plates (called a capacitor) separated by a distance of d and a positively charged sphere directly in the middle of the two plates.  The upper plate has a positive charge, and the lower plate has a negative charge.

In which direction should the charged sphere move to increase the energy stored in the system?

Scientists studied the extent of Arctic sea ice from 1978 to 2016.  Observations from selected years are shown in the maps.  The white areas show the extent of the sea ice in November of the indicated year.  The dark blue areas are ice-free oceans, and the green areas are continents in all of the maps.

Based on the Arctic sea ice images from 1978 to 2016, what is most likely going to occur from 2017 to 2027?

A student is asked to evaluate two different bumper designs that will be used on bumper cars at a local amusement park. The bumpers have the same mass and are each attached to a test car that undergoes a controlled collision with a wall. The student measures the average impact of force on each bumper during the collision and the duration of each collision. The student's results are shown in the table.

Which design will provide better protection for a rider in a collision, and why?

Students in a class are designing an investigation to determine the effect running on a treadmill has on heart rate. They decide to have several students run for 20 minutes on a treadmill.

Which two data sets must the students collect in order to determine the effect exercise has on heart rate?

A railroad car with a mass of 90,000 kg is traveling along a straight, horizontal track at a constant speed of 2 m/s. The car collides with a second railroad car, also with a mass of 90,000 kg, that is initially at rest. The railroad cars stick together after the collision, as shown in the figure.

What is the speed of the two railroad cars immediately after the collision?

A block with a mass of m is sliding to the right with a velocity of v on a horizontal, frictionless surface. It has a head-on collision with a larger block with a mass of 9m that is initially at rest. After the collision, the blocks are stuck together and move to the right, along the same path, with a velocity of 0.1v.

Which two statements are correct about the forces exerted on the blocks during the collision?