# Energy, Impulse & Collisions

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### 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

### 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

### How to Convert Potential Energy into Kinetic Energy

When an object falls, its gravitational potential energy is changed to kinetic energy. You can use this relationship to calculate the speed of the object’s descent. Gravitational potential energy for a

### The Principle of Conservation of Mechanical Energy

In physics, if you know the kinetic and potential energies that act on an object, then you can calculate the mechanical energy of the object. Imagine a roller coaster car traveling along a straight stretch

### Use the Principle of Conservation of Mechanical Energy to Find an Object’s Final Speed

Thanks to the principle of conservation of mechanical energy, you can use physics to calculate the final speed of an object that starts from rest.

“Serving as a roller coaster test pilot is a tough gig,

### Use the Principle of Conservation of Mechanical Energy to Find the Final Height of a Moving Object

Thanks to the principle of conservation of mechanical energy, you can use physics to determine the final height of a moving object. At this very moment, for example, suppose Tarzan is swinging on a vine

### How to Calculate the Kinetic Energy of an Object

You can use physics to calculate the kinetic energy of an object. When you start pushing or pulling a stationary object with a constant force, it starts to move if the force you exert is greater than the

### How to Calculate Changes in Kinetic Energy Using Net Force

In physics, if you want to find the change in an object’s kinetic energy, you have to consider only the work done by the net force acting on the object. In other words, you convert only the work done by

### How to Calculate the Torque Needed to Accelerate a Spinning Disc

You can use physics to calculate the amount of torque needed to accelerate (or decelerate) the speed of a spinning disc. Without the ability to change the speed of a disc, it would be impossible for you

### Storing Your Energy: Potential Energy

Objects can have energy at rest simply by having a force act on them. For example, an object at the end of a stretched spring has energy because when you let the object go and it accelerates because of

### Power Problems in Physics

When it comes to work in physics, you’re sure to see problems involving power, which is the amount of work being done in a certain amount of time. Here’s the equation for power,

### What Is Impulse in Physics?

When you apply a force for a certain amount of time, you create an impulse. In fact, that's the definition of impulse — impulse equals the force applied multiplied by the time it was applied. Here's the

### Momentum in Physics

Momentum is the most important quantity when it comes to handling collisions in physics. Momentum is a physical quantity defined as the product of mass multiplied by velocity. Note the definition says

### What Is Kinetic Energy?

When you have objects in motion, you have kinetic energy. When, for example, you slide an object on a frictionless surface, the work you do goes into the object’s kinetic energy:

### Relating Impulse and Momentum

It turns out that there’s a direct connection between impulse and momentum. If you hit a pool ball with a cue, the cue imparts a certain impulse to the ball, causing the ball to end up with a particular

### Conserving Momentum

The major tool you have in calculating what’s going to happen in collisions is the knowledge that momentum is conserved. You know that the total momentum before the collision is the same as the total momentum

### Conserving Kinetic Energy

In some types of collisions, called elastic collisions,kinetic energy and momentum are conserved. What do elastic collisions look like? In general, there’s no permanent deformation of any of the objects

### Collisions in Two Dimensions

Collisions can take place in two dimensions. For example, soccer balls can move any which way on a soccer field, not just along a single line. Soccer balls can end up going north or south, east or west