Calculating torque

• 1). Consider a door. A force f is required to open the door. Where the force is applied and how much force is applied determines whether the door is rotated about its hinges. In order to move the door most easily a force must be applied at a 90-degree angle to the door. The doorknob is located as far from the hinges, or the axis of rotation r as possible. Knowing the amount of force f, the axis of rotation r and the angle between f and r is necessary in determining torque.
  
  
• 2). Measure the length of r. That is the distance between the point of rotation and the point where the force f is applied. Record the length.
  
  
• 3). Multiply r by the predetermined f and the sine of the angle between r and f. For example, applying f = 50 newtons at a distance of r = .5 meters with an angle of 30 degrees between f and r results in the equation: torque = .5 * 50(sin(30)) = 12.5 newton/meter. This means the torque is 12.5 newtons of force per meter.
  
  

Calculating speed

• 1). Consider an object at rest. Once the object begins to move, measure the amount of time it takes for the object to come to a stop. For example, consider an object in motion for 45 seconds.
  
  
• 2). Measure the distance the object traveled while in motion. For example, our object has been in motion for 45 seconds and is now measured to have moved 18 meters.
  
  
• 3). Divide the distance the object traveled by the amount of time it takes for the object to come to rest. For example, the equation for our object becomes (18 / 45) = .4 meters/second. So, the speed of our object is .4 meters per second.
  
  

Calculating power

• 1). Determine the amount of work a force does on an object. Work is determined by multiplying the amount of force by the distance the object travels by the cosine of the angle between the force and the distance. For example, the work done by a force of 100 newtons that moves an object 35 meters horizontally is defined by the equation: work = 100 newtons * 35 meters * cos(0) = 3,500 newtons/meter.
  
  
• 2). Measure the amount of time the force is applied. For example, our object stays in motion for 35 seconds while 3,500 newtons per meter of work is performed on it by a force.
  
  
• 3). Divide the work done by the amount of time the work was applied. Power is measured in units called joules. For example, the equation of our object becomes: power = (3,500 / 35) = 100 joules per second. This is the average power caused by the applied force during the 35 seconds.