Speed, Motion & Acceleration

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How to Calculate an Object’s Velocity Based on Its Displacement

In physics, velocity, which is the rate of change of position (or speed in a particular direction), is a vector. Imagine that you just hit a ground ball on the baseball diamond and you’re running along [more…]

Newton’s First Law: How Inertia Works

In physics, Newton’s laws explain what happens with forces and motion, and his first law states, “An object continues in a state of rest, or in a state of motion at a constant velocity along a straight [more…]

Newton's Second Law: How Net Force, Mass, and Acceleration Affect Motion

Newton’s first law says that an object remains in uniform motion unless acted on by a net force. When a net force is applied, the object accelerates. Newton’s second law details the relationship between [more…]

Newton's Third Law: Action and Reaction

Newton’s third law of motion is famous, especially in wrestling and drivers’ ed circles, but you may not recognize it in all its physics glory: “Whenever one body exerts a force on a second body, the second [more…]

How to Calculate Acceleration

In physics terms, acceleration, a, is the amount by which your velocity changes in a given amount of time. Given the initial and final velocities, vi and [more…]

Understanding Positive and Negative Acceleration

In physics calculations, acceleration — just like displacement and velocity — can be positive or negative. The sign of the acceleration tells you whether you’re speeding up or slowing down [more…]

How Positive and Negative Acceleration Relate to Speed and Velocity

In physics, the sign of an object’s acceleration depends on its direction. If you slow down to a complete stop in a car, for example, and your original velocity was positive and your final velocity was [more…]

How to Calculate Time and Distance from Acceleration and Velocity

In a physics equation, given a constant acceleration and the change in velocity of an object, you can figure out both the time involved and the distance traveled. For instance, imagine you’re a drag racer [more…]

Finding Distance Using Initial Velocity, Time, and Acceleration

In a physics equation, given initial velocity, time, and acceleration, you can find an object’s displacement. Here’s an example: There you are, the Tour de France hero, ready to give a demonstration of [more…]

What Is a Vector?

In physics, when you have a vector, you have to keep in mind two quantities: its direction and its magnitude. Quantities that have only a magnitude are called [more…]

Calculating the Resultant Vector of Two Displacement Vectors

In physics, just as you can add two numbers to get a third number, you can add two vectors to get a resultant vector. To show that you’re adding two vectors, put the arrows together so that one arrow starts [more…]

How to Subtract Vectors

You don’t come across vector subtraction very often in physics problems, but it does pop up. To subtract two vectors, you put their feet (or tails, the non-pointy parts) together; then draw the resultant [more…]

How to Add Vectors on a Grid

You can use the components of vectors to add vectors together using a grid. Doing so reduces the problem of adding vectors to a simple combination of adding numbers together, which is very useful when [more…]

How to Find Vector Components

In physics, when you break a vector into its parts, those parts are called its components. For example, in the vector (4, 1), the x-axis (horizontal) component is 4, and the [more…]

How to Calculate the Displacement of an Object Moving in Two Dimensions

In physics, displacement, which is a change in position, has a magnitude and a direction associated with it. When you have a change of position in a particular direction and of a particular distance, these [more…]

How Adding Enough Force Can Overcome Friction

In physics, because of Newton’s third law, whenever you apply a force to an object, say, by pulling it, the object applies an equal and opposite force on you. Here’s an example that lets you work out how [more…]

Calculating Equilibrium Where the Net Force on an Object Is Zero

In physics, an object is in equilibrium when it has zero acceleration — when the net force acting on it is zero. The object doesn’t actually have to be at rest, as in the example below, which uses a pulley [more…]

How Gravity Affects the Acceleration of an Object on an Inclined Plane

You can use physics to determine how gravity affects the acceleration of an object as it moves along an inclined plane. When you’re on or near the surface of the Earth, the pull of gravity is constant. [more…]

Finding the Force of Gravity along an Inclined Plane

You can use physics to determine the force of gravity on an object that moves along an inclined plane. You can break the weight of the object down into components that are parallel to and perpendicular [more…]

Finding the Velocity of an Object Moving along an Inclined Plane

In physics, you can calculate the velocity of an object as it moves along an inclined plane as long as you know the object’s initial velocity, displacement, and acceleration. Just plug this information [more…]

How to Calculate the Maximum Height of a Projectile

According to the laws of physics, when a projectile flies into the air, its trajectory is shaped by Earth’s gravitational pull. Because the force of gravity only acts downward — that is, in the vertical [more…]

How to Calculate How Long a Projectile Is Airborne

When you launch a projectile into the air, you can use physics to determine how long it will remain airborne. Because the force of gravity only acts downward — that is, in the vertical direction — you [more…]

Calculating the Speed of an Object with Uniform Circular Motion

An object with uniform circular motion travels in a circle with a constant speed. Outside a physics class, practical examples may be hard to come by, unless you see a race car driver on a perfectly circular [more…]

Relating Linear and Angular Motion

In physics, just as you can use formulas to calculate linear velocity, acceleration, displacement, and motion, you can also use equivalent formulas for angular [more…]

How to Calculate a Satellite’s Speed around the Earth

In space, gravity supplies the centripetal force that causes satellites (like the moon) to orbit larger bodies (like the Earth). Thanks to physics, if you know the mass and altitude of a satellite in orbit [more…]


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