Work Mechanical Advantage and Simple Machines Work The

Work, Mechanical Advantage and Simple Machines

Work The work done by a constant force of magnitude F on a point that moves a displacement d in the direction of the force is the product, W = Fd where W is work, F is force and d is distance. Unit of work is the newton-meter or Joule 1 Nm = 1 joule

Example If a force of 10 newtons (F = 10 N) acts on a point that travels 2 meters (d = 2 m), then it does the work W = (10 N)(2 m) = 20 Nm = 20 J. This is approximately the work done lifting a 1 kg weight from the ground to over a person's head against the force of gravity.

Mechanical Advantage In physics and engineering, mechanical advantage (MA) is the factor by which a machine multiplies the force put into it. It trades off forces against movement to obtain a desired amplification in the output force over the input force.

Inclined Plane (Ramp) Mechanical Advantage (MA) MA = Length/Rise Wout = Win Wout = Fg x Rise Win = Fi x Length MA = Fg/Fi = Length/Rise Fi = Fg x Rise/Length Example: For Rise = 1 and Length = 2 MA = 2 Fi = ½ F g

Screw Inclined plane where flights are on an angle forming a continuous ramp around the central shaft. This makes the screw easier to turn against a given resistance.

Lever F 1 x D 1 = F 2 x D 2 In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object. MA = length of effort arm ÷ length of resistance arm = D 2 ÷ D 1

Wheel and Axle Wheel Axle Lever with D 2 = radius of wheel and D 1 = radius of axel

Energy is the capacity of a system to do work. The unit of energy is the joule or newton-meter (same as work). Remember work = force x distance

Example If a person pushes an object x meters against an opposing force of F newtons, Fx joules (newton-meters) of work has been done on the object. The person's body has lost Fx joules of energy and the object has gained Fx joules of energy.

Example If a force of 10 newtons (F = 10 N) acts on a point that travels 2 meters (d = 2 m), then it does the work W = (10 N)(2 m) = 20 Nm = 20 J. This is approximately the work done lifting a 1 kg weight from the ground to over a person's head against the force of gravity. F = ma = 1 kg x 10 m/s 2 = 10 N The person’s body has lost 20 J of energy and the weight has gained 20 J of (potential) energy.