Medium ACT Physics Practice Questions

Concept Explanation

Medium ACT Physics Practice Questions focus on the fundamental laws of motion, energy conservation, and basic thermodynamics that appear within the Science section of the exam. Unlike the SAT, the ACT does not have a standalone physics test; instead, physics concepts are integrated into the Science reasoning passages. To succeed, you must understand how variables such as force, mass, and acceleration interact, often described by Newton's Second Law. These questions typically require you to interpret data from experiments or apply basic formulas to predict the outcome of a physical system. Mastery of this level involves moving beyond simple observation to understanding the underlying relationships, such as how kinetic energy changes with velocity or how electrical circuits function according to Ohm's Law.

For students looking to build a solid foundation, reviewing ACT Prep resources can help clarify how these scientific principles are tested. You will frequently encounter scenarios involving gravity, friction, and heat transfer. The ACT expects you to recognize that as an object falls, its potential energy converts to kinetic energy, or that the total energy in a closed system remains constant. Developing a mental toolkit of these relationships allows you to solve problems quickly without needing a deep background in advanced calculus-based physics.

Solved Examples

1. Force and Acceleration: A 5 kg block is pushed across a frictionless surface with a constant force of 20 Newtons. What is the acceleration of the block?
   1. Identify the relevant formula: $$F = ma$$
   2. Substitute the known values into the equation: $$20 \text{ N} = 5 \text{ kg} \times a$$
   3. Solve for $a$: $$a = \frac{20}{5} = 4 \text{ m/s}^2$$
   4. The acceleration is $4 \text{ m/s}^2$.
2. Work and Energy: How much work is done when a person lifts a 10 kg box to a height of 2 meters? (Assume $g = 9.8 \text{ m/s}^2$)
   1. The work done against gravity is equal to the change in potential energy: $$W = mgh$$
   2. Plug in the values: $$W = 10 \text{ kg} \times 9.8 \text{ m/s}^2 \times 2 \text{ m}$$
   3. Calculate the result: $$W = 196 \text{ Joules}$$
   4. The work done is 196 J.
3. Ohm's Law: A circuit has a resistance of $50 \text{ }\Omega$ and a voltage source of 100 V. What is the current flowing through the circuit?
   1. Recall Ohm's Law: $$V = IR$$
   2. Rearrange the formula to solve for current ($I$): $$I = \frac{V}{R}$$
   3. Substitute the values: $$I = \frac{100}{50}$$
   4. The current is 2 Amperes.

Practice Questions

1. A car travels at a constant speed of 30 m/s for 15 seconds. What is the total distance traveled by the car?

2. A spring with a spring constant ($k$) of 200 N/m is compressed by 0.1 meters. What is the elastic potential energy stored in the spring?

3. If the temperature of a gas is held constant while its volume is halved, what happens to the pressure of the gas according to Boyle's Law?

4. An object of mass 2 kg is moving with a velocity of 4 m/s. What is its kinetic energy?

5. A light ray passes from air into water. If the angle of incidence is $30^\circ$, will the angle of refraction be greater than, less than, or equal to $30^\circ$?

6. Calculate the gravitational force between two 10 kg masses separated by a distance of 1 meter. (Use $G = 6.67 \times 10^{-11} \text{ N}\cdot \text{m}^2/ \text{kg}^2$)

7. A 60-watt light bulb is left on for 2 hours. How much energy in Joules does it consume?

8. A wave has a frequency of 10 Hz and a wavelength of 5 meters. What is the speed of the wave?

9. According to the scientific method, if an experiment yields results that contradict a hypothesis, what should the researcher do next?

10. A 5 kg object is dropped from a height. If air resistance is negligible, what is its acceleration after 2 seconds of falling?

Answers & Explanations

1. 450 meters. Using the formula $$d = vt$$, we multiply the velocity (30 m/s) by the time (15 s) to get 450 m.
2. 1 Joule. The formula for elastic potential energy is $$PE_s = \frac{1}{2}kx^2$$. Plugging in the values: $$\frac{1}{2}(200)(0.1)^2 = 100 \times 0.01 = 1$$.
3. The pressure doubles. Boyle's Law states that $P_1V_1 = P_2V_2$. If volume is halved, pressure must double to keep the product constant.
4. 16 Joules. Kinetic energy is calculated using $$KE = \frac{1}{2}mv^2$$. Here, $$\frac{1}{2}(2)(4^2) = 1 \times 16 = 16$$.
5. Less than $30^\circ$. When light moves from a less dense medium (air) to a more dense medium (water), it bends toward the normal, resulting in a smaller angle of refraction.
6. $6.67 \times 10^{-9} \text{ N}$. Using Newton's Law of Universal Gravitation: $$F = G\frac{m_1m_2}{r^2} = (6.67 \times 10^{-11}) \frac{10 \times 10}{1^2} = 6.67 \times 10^{-9}$$.
7. 432,000 Joules. Power is energy per unit time ($P = E/t$). Energy is $$60 \text{ W} \times (2 \text{ hours} \times 3600 \text{ s/hour}) = 60 \times 7200 = 432,000$$.
8. 50 m/s. Wave speed is found using $$v = f\lambda$$. Multiplying frequency (10 Hz) by wavelength (5 m) gives 50 m/s.
9. Revise or reject the hypothesis. In science, data dictates the validity of a hypothesis. If the data doesn't match, the hypothesis must be adjusted. Check out experimental design tips for more on this.
10. $9.8 \text{ m/s}^2$. Near the Earth's surface, all objects in free fall accelerate at a constant rate of approximately $9.8 \text{ m/s}^2$, regardless of how long they have been falling.

1. Which of the following best describes the relationship between the mass of an object and its acceleration when a constant net force is applied?

• AAcceleration is directly proportional to mass
• BAcceleration is inversely proportional to mass
• CAcceleration is equal to mass squared
• DAcceleration is independent of mass

Frequently Asked Questions

How much physics is actually on the ACT Science section?

Physics typically makes up about 15-20% of the Science section, usually appearing in one or two dedicated passages. While you don't need to memorize advanced equations, knowing basic concepts like density, force, and energy is highly beneficial.

Do I need to memorize formulas for the ACT?

The ACT Science section is primarily a test of logic and data interpretation, so most necessary information is provided in the text or graphs. However, knowing basic formulas like density ($\text{mass/volume}$) or speed ($\text{distance/time}$) can save you valuable time. You can use an AI Question Generator to practice these specific types of calculations.

What is the most common physics topic tested?

Mechanics, specifically Newton's Laws and energy conservation, is the most frequently tested area. Questions often ask how changing one variable, like mass or height, affects another, like speed or impact force.

Can I use a calculator on the ACT Science section?

No, calculators are only permitted on the Math section of the ACT. Any math required in the Science section will involve simple arithmetic, estimation, or reading values directly from ACT graphs.

How can I improve my speed on physics-based passages?

Focus on identifying the relationship between variables (direct or inverse) in the provided tables and charts. Often, you can answer the question by observing trends without performing any complex physics calculations. Using a AI Exam Simulator can help you get used to the pacing required for these passages.