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### How to Calculate Power Based on Work and Time

Sometimes, it isn’t just the amount of work you do but the rate at which you do work that’s important. In physics, the concept of power gives you an idea of how much work you can expect in a certain amount [more…]

### Relating Impulse and Momentum through the Impulse-Momentum Theorem

In physics, you can connect the impulse you give to an object — like striking a pool ball with a cue — with the object’s change in momentum; all you need is a little algebra and a process called the [more…]

### How to Calculate Force from Impulse and Momentum

In physics, you can use the impulse-momentum theorem to calculate force based on impulse and momentum. For example, you can relate the impulse with which you hit an object to its consequent change in momentum [more…]

### How the Principle of Conservation of Momentum Works

In physics, the *principle of conservation of momentum*states that when you have an isolated system with no external forces, the initial total momentum of objects before a collision equals the final total [more…]

### How to Find the Velocity of Two Objects after Collision

You can use the principle of conservation of momentum to measure characteristics of motion such as velocity. Say, for example, that you’re out on a physics expedition and you happen to pass by a frozen [more…]

### How to Determine Whether a Collision Is Elastic or Inelastic

In physics, collisions can be defined as either elastic or inelastic. When bodies collide in the real world, they sometimes squash and deform to some degree. The energy to perform the deformation comes [more…]

### How to Calculate Velocities of Two Objects with Different Masses after an Elastic Collision

When a collision between two objects is elastic, kinetic energy is conserved. In physics, the most basic way to look at elastic collisions is to examine how the collisions work along a straight line. If [more…]

### How to Change Equations from Linear Motion to Rotational Motion

In physics, when you go from linear motion to rotational motion, you need to change the equations that you use to calculate your results. Here are the angular equivalents [more…]

### Calculating Tangential Velocity on a Curve

When an object moves in a circle, if you know the magnitude of the angular velocity, then you can use physics to calculate the tangential velocity of the object on the curve. [more…]

### How to Calculate Torque Perpendicular to Where Force Is Applied

In physics, how much torque you exert on an object depends on two things: the force you exert, *F*; and the *lever arm.* Also called the *moment**
**arm*, the lever arm is the perpendicular distance from the pivot [more…]

### How to Convert Linear Force to Angular Torque

Using physics, you can convert linear force to angular torque. For example, say that you’re whirling a ball in a circle on the end of a string, as shown in the figure. You apply a tangential force [more…]

### How to Calculate the Momentum of Inertia for Different Shapes and Solids

In physics, when you calculate an object’s moment of inertia, you need to consider not only the mass of the object but also how the mass is distributed. For example, if two disks have the same mass but [more…]

### How to Calculate the Potential and Kinetic Energy in a Spring

In physics, you can examine how much potential and kinetic energy is stored in a spring when you compress or stretch it. The work you do compressing or stretching the spring must go into the energy stored [more…]

### How to Calculate the Angular Frequency of a Mass on a Spring

In physics, you can apply Hooke’s law, along with the concept of simple harmonic motion, to find the angular frequency of a mass on a spring. And because you can relate angular frequency and the mass on [more…]

### How to Calculate a Spring Constant Using Hooke's Law

Any physicist knows that if an object applies a force to a spring, then the spring applies an equal and opposite force to the object. Hooke’s law gives the force a spring exerts on an object attached to [more…]

### How to Calculate Angular Momentum

In physics, you can calculate angular momentum in the same way that you calculate linear momentum — just substitute moment of inertia for mass, and angular velocity for velocity. [more…]

### Calculating Rotational Kinetic Energy on a Ramp

In physics, objects can have both linear and rotational kinetic energy. This can occur when an object rolls down a ramp instead of sliding, as some of its gravitational potential energy goes into its linear [more…]

### How to Calculate Rotational Kinetic Energy

If you put a lot of work into rotating an object, the object starts spinning. And when an object is spinning, all its pieces are moving, which tells a physicist that it has kinetic energy. For spinning [more…]

### How to Calculate Rotational Work

In physics, one major player in the linear-force game is *work*; in equation form, work equals force times distance, or *W* = *Fs*. Work has a rotational analog. To relate a linear force acting for a certain [more…]

### Calculating How Far an Object Will Slide Down an Inclined Surface

You can use physics to calculate how far an object will slide down an inclined surface, such as a ramp. For example, say you and your friends are pushing a refrigerator up a ramp onto a moving van, when [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…]

### Measuring Force and Direction Using Vector Addition

In physics, to take angles (or direction) into account when measuring force, you need to do a little vector addition. Take a look at the following figure. Here, the mass [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 Friction Slows Movement

Friction is an important concept in physics. It’s the force that hinders two materials from sliding past each other. Friction is essential for everyday living. Imagine a world without friction: no way [more…]

### How Friction Relates to Normal Force

According to the laws of physics, the force of friction, *F*_{friction}*,* always acts to oppose the force you apply when you try to move an object. Friction is proportional to the force with which an object [more…]