Physics Pressure

Worded content on the PowerPoint on Centripetal Force By Army Seals Introduction Centripetal Force What is it? It is a force which acts on a body moving in a circular path and is directed towards the centre around which the body is moving. A diagram of centripetal force Centrifugal Vs Centripetal A labelled diagram depicting the difference of the two. Centrifugal Force This is the reacting force that makes objects move outwards when they are spinning around something or travelling in a curve. A diagram of centrifugal force Calculating Centripetal Force Fc=mv2/r and what each part of the formula was illustrated in a picture What are Examples? Pictures of a car turn a corner at high speed, children on a round around, and a man swinging a ball in circles using a rope. What is efficiency? This is the state of achieving maximum productivity with minimum wasted effort or expense. Efficiency of Machines This is the work done by a machine which is expressed in a ratio between the input and output effort, measured in percentage. How to calculate it? To calculate the efficiency of a machine, divide the output work by the input work and multiply the result by 100 percent. A picture of the formula was displayed. An example was given. Mechanical Advantage This is a measurement of the force amplification achieved by using a tool, mechanical device or machine system. In other words, it is the ratio of the output force (load) of a machine to the input force (effort). An example was given. Velocity Ratio

This is the ratio of the distance moved by the point at which the effort is applied, in a machine, to the distance moved by the point at which the load is applied, in the same time. It is also called the distance ratio. A picture of the formula was displayed Worded part of the examples Incline Planes VR = Displacement moved by effort/Displacement by load =10m/2m =5 Single Fixed Pulley VR = Displacement moved by effort /Displacement by load = 10m/ 10m =1 Note: Although the work wasn’t made easier, it is convenient as the force is inverted. Single Movable Pulley VR = Displacement moved by effort /Displacement by load = (5m + 5m)/ 5m =10m/5m =2 Block and Tackle

VR = Displacement moved by effort /Displacement by load = 30m / 10m =3 Slowing Gears VR = Displacement moved by effort /Displacement by load = 1rev.(25/25teeth) / 1/3rev. (25/75teeth) =1: (1/3) =0.333

Therefore, it would take 3 rev. of the smaller gear to turn 1 rev. of the larger gear, slowing down the machine. Speeding Gears VR = Displacement moved by effort /Displacement by load = 1rev.(40/40teeth) / 2rev. (40/20teeth) =1:2 =0.5 Therefore, it would take 1/2 rev. of the larger gear to turn 1 rev. of the smaller gear, speeding up the machine. Hydraulic lift VR = Displacement moved by effort /Displacement by load = 100m/50m =2:1 =2