AP Physics 2 Midterm Review

A system absorbs 100 J of heat and does 200 J of work on a piston. What is the change in internal energy?

• -100 J

• -300 J

• 100 J

• 300 J

Tags

NGSS.HS-PS3-1

Which of these units is the equivalent of a Pascal?

• N*m²

• N/m²

• N+m²

• N-m²

Answer explanation

A Pascal (Pa) is defined as one Newton per square meter, which is represented as N/m². This makes N/m² the correct equivalent unit for a Pascal.

A gas at 20Pa expands a container from 10m³ to 20m³. How much work is done by the gas?

• -400 J

• 350 J

• 600 kJ

• -200 J

Answer explanation

The work done by the gas during expansion is calculated using the formula W = -PΔV. Here, P = 20 Pa and ΔV = 20m³ - 10m³ = 10m³. Thus, W = -20 Pa * 10m³ = -200 J, confirming the correct answer is -200 J.

The Gulf Stream is a current that brings warm ocean water from the south to the north is which form of thermal transfer?

• conduction

• convection

• radiation

Answer explanation

The Gulf Stream transfers warm water through convection, which involves the movement of fluid (water) due to temperature differences. Conduction and radiation do not apply to the movement of water in this context.

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

Entropy increases from solid, liquid, to gas. Why?

• Molecular disorder increases

• Molecular randomness decreases

• Molecules are more energetic

• Molecules are more reactive

Answer explanation

Entropy increases from solid to gas because molecular disorder increases. In solids, molecules are tightly packed and ordered, while in gases, they are more spread out and random, leading to higher entropy.

Tags

NGSS.HS-PS3-4

When thermal energy is added to a substance, the substance's particles move:

• More rapidly at an increased distance from each other.

• More rapidly with less distance between each other.

• More slowly with a greater distance between each other.

• More slowly with a reduced distance between each other.

Answer explanation

When thermal energy is added, particles gain energy and move more rapidly. This increased motion causes them to spread apart, resulting in greater distances between them, making 'More rapidly at an increased distance from each other' the correct choice.

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

One mole of an ideal gas is taken through a closed cycle represented by this PV diagram. If going from point 1 to 2 is isothermal, what is true about the change in internal energy and heat going from point 2 to 3?

• ΔU = 0, Q > 0

• ΔU > 0, Q > 0

• ΔU < 0, Q < 0

• ΔU < 0, Q > 0

Answer explanation

From point 2 to 3, the gas expands adiabatically, leading to a decrease in internal energy (ΔU < 0) and since work is done by the gas, heat is also released (Q < 0). Thus, the correct choice is ΔU < 0, Q < 0.

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

The change of state of an ideal gas is represented on the PV diagram shown here. What is true about the work done for each section? Choose all that are correct!

• The work is equal for all cycles

• Work for 1→2 = Work for 2→3

• No work is done for 1→2 or 3→4

• Work for 2→3 is 3 times larger than 4→1

Answer explanation

No work is done for isothermal processes (1→2 and 3→4) as there is no change in volume. The work for 2→3 is larger than 4→1 due to the area under the curve, confirming it is 3 times larger.

Find the temperaure of 2 moles of an ideal gas which is at a pressure of 10 kPa and has a volume of 0.5 m³.

• 300 K

• 90 K

• 300 ºC

• 600 K

Answer explanation

Using the ideal gas law, PV = nRT, we can rearrange to find T: T = PV/(nR). With P = 10 kPa, V = 0.5 m³, n = 2 moles, and R = 8.314 J/(mol·K), we calculate T = 300 K, confirming the correct answer is 300 K.

What is the thermodynamic cycle from point 3→1 in the diagram above?

• isobaric

• isothermal

• isochoric

• isometric

Answer explanation

The transition from point 3 to 1 occurs at constant volume, meaning the volume does not change while the pressure and temperature may vary. This defines an isochoric process, making it the correct choice.