Physics I

Action-reaction forces appear when two carts interact through collisions, pushing, or pulling. The carts used in this experiment have variable masses, which lets students compare how the forces change in different situations.

The first part looks at two wheeled carts as they collide. The goal is to find when the force one cart exerts on the other has the same magnitude as the force the second cart exerts back on the first. It also examines when those two forces have different magnitudes.

The...

Newton’s second law links force and motion. In this experiment, students measure the acceleration of a glider as it is acted on by a force. The setup shows how motion changes when a net force is applied.

The activity also connects to Isaac Newton’s three laws of motion. The first law explains that objects in motion tend to stay in motion. The second law explains that objects accelerate when a net force acts on them. The third law states that every force has an equal and opposite force.

The...

Vectors are quantities with both magnitude and direction. In this experiment, vector addition and subtraction are shown in multiple directions. The goal is to calculate the result of several vectors and then check those results in the lab.

A vector has a size, or magnitude, and a direction. The magnitude is shown by the length of the vector. The direction is usually given by the angle it makes with the x-axis. These ideas help describe how vector quantities combine.

Forces are vectors, so...

Projectile motion can be used to study kinematics in one and two dimensions. In this lab, a projectile is launched straight up to examine motion in 1 dimension under constant acceleration. The maximum height is measured and compared with the kinematic equations for upward motion.

The experiment also shows motion in 2 dimensions by launching the ball at an angle theta. From the initial speed, total time, and angle of trajectory, the landing distance can be predicted with kinematic equations.

Gravity on Earth can be measured through gravitational acceleration, often written as g. This value describes the acceleration an object experiences on Earth because of Earth’s gravitational force. Knowing g is important because it tells us the strength of that force at Earth’s surface.

The idea comes from Isaac Newton’s work on gravity. A famous story says he saw an apple fall from a tree and noticed its acceleration. That observation led him to think that a force was acting on the apple, and...

Momentum in low-friction collisions is tested by comparing the motion of objects before and after they collide. A surface with very little friction is used so the moving objects can be studied more clearly. Their initial momentum and final momentum are measured during the collision.

Momentum conservation is one of the most important laws in physics. In physics, something is conserved when the initial value equals the final value. For momentum, this means the total initial momentum of a system...

Friction is a force that opposes motion between two surfaces. This experiment examines the two main kinds of friction: static friction and kinetic friction. It also shows how to measure the coefficients of friction for objects sliding on a flat surface and down an inclined plane.

Static friction acts when an object is not moving. A force must first be applied to start the object moving. Kinetic friction acts after motion begins. It slows a sliding object as the surfaces move past each other.

Spring potential energy is a key idea in physics. It is the energy stored when a spring is stretched or compressed from its relaxed state. Because the spring can do work on an object, that stored energy is an important example of potential energy.

Potential energy is the energy linked to forces that depend on an object’s position relative to its surroundings. Gravitational potential energy depends on height above the ground, and it is covered in another video. Spring potential energy depends...

Equilibrium in mechanics is a special case where an object or system has both zero net force and zero net torque. When that happens, linear acceleration and angular acceleration are also zero. The object may stay at rest, or its center of mass may move at a constant velocity.

Even in equilibrium, forces can still act on an object. In fact, there are very few situations on Earth where no forces act at all. A person walking across a bridge is a simple example. The person pushes downward on the...

Torque describes rotational force and how it acts in a system. It is the force that causes rotational acceleration, much as force causes linear acceleration. In this experiment, students learn the parts of torque and how they work together.

Torque is defined as the product of a force and the distance of that force from the axis of rotation. The axis of rotation is the point or line around which an object turns. A larger force or a greater distance from the axis can change the size of the...

Rotational inertia describes how strongly an object resists changes in its spin. In linear motion, inertia is tied to mass. A more massive object needs more force to accelerate, and this idea is shown by Newton’s second law, where force equals mass times acceleration.

For rotation, the same basic idea applies. Rotational inertia is the resistance of an object to being rotationally accelerated. It depends on mass and on how far that mass is from the center of rotation. Mass placed farther from...

Angular momentum in rotating systems depends on an object’s moment of inertia and its angular velocity. It is the rotational form of linear momentum. In this experiment, students examine how this quantity describes motion in a spinning object.

Angular momentum is conserved. That means the total angular momentum of a system does not change if no external torques act on it. Torque is the rotational equivalent of force. Because of this conservation rule, angular momentum is an important quantity...

Gravity, kinetic energy, and work are connected in this high school physics experiment. The activity shows the work-energy principle using a glider on an air track. It focuses on how gravitational potential energy changes into translational kinetic energy as the glider moves.

Gravitational potential energy is the energy an object has because of its position in a gravitational field. An object placed higher above the ground has more gravitational potential energy. Translational kinetic energy...

Heat flow and the first law of thermodynamics explain how energy moves between objects at different temperatures. When a pot of water sits on a hot stove, heat flows from the stove to the water. This transfer continues until the temperatures tend to equalize.

The same idea appears when objects are in thermal contact. Heat moves spontaneously from the hotter object to the colder one. For example, if ice cubes are added to a cup of room-temperature water, heat from the water flows to the ice.

Entropy is a key idea in thermodynamics, the study of heat and energy. It connects to the second law of thermodynamics, which says that the entropy of a system always increases over time or stays constant in ideal cases. That constant change can happen in a steady state or during a reversible process.

When a system undergoes an irreversible process, its entropy will always increase. In this case, the change in entropy, written as ΔS, is greater than or equal to zero. This rule helps describe...