Speed D. Crowley, 2008

Speed To be able to calculate speed Saturday, January 30, 2016

Forces  How can we represent forces?  What forces help movement?  Which hinder it?  How can we represent forces?  What forces help movement?  Which hinder it?  What are contact and non-contact forces?  What type of forces are there?  What are contact and non-contact forces?  What type of forces are there?

Forces A force is a push or a pull upon an object Contact forces - two objects in contact with each other Non-contact forces - a force that acts over a distance A force is a push or a pull upon an object Contact forces - two objects in contact with each other Non-contact forces - a force that acts over a distance Gravity - non-contact forceFriction (via brake discs) - contact force

Arrows  Arrows are drawn to represent forces  These arrows always work in pairs - if there is a force one way, there will be an opposite force the other way  The bigger the arrow, the bigger the force  Look at the following, and see if you can decide where the force arrows should be…  Arrows are drawn to represent forces  These arrows always work in pairs - if there is a force one way, there will be an opposite force the other way  The bigger the arrow, the bigger the force  Look at the following, and see if you can decide where the force arrows should be… Apple, on a deskStationary carSpace shuttle, accelerating upwards

Types Of Force Gravitational Force - acting straight downwards Magnetic Force - push / pull exerted by a magnet Electrical Force - a force between two charged objects Reaction Force - force from the surface, usually acting straight upwards Contact Force (push / pull forces) - force which results in the object speeding up, for example, due to an engine / rocket Friction - friction between surfaces slowing an object down. This can include air resistance - (special type of frictional force) where air in the atmosphere slows down a moving object Tension Force - pulling of a rope / cable from opposite ends Elastic Force - compression / extension of a spring or elastic product Gravitational Force - acting straight downwards Magnetic Force - push / pull exerted by a magnet Electrical Force - a force between two charged objects Reaction Force - force from the surface, usually acting straight upwards Contact Force (push / pull forces) - force which results in the object speeding up, for example, due to an engine / rocket Friction - friction between surfaces slowing an object down. This can include air resistance - (special type of frictional force) where air in the atmosphere slows down a moving object Tension Force - pulling of a rope / cable from opposite ends Elastic Force - compression / extension of a spring or elastic product

Forces  Look at the diagram of the stationary car, car at steady speed, and accelerating car  How can we draw force arrows to represent this?  Look at the diagram of the stationary car, car at steady speed, and accelerating car  How can we draw force arrows to represent this? Car moving at a steady speed (balanced force) Car stationary (balanced force) Car accelerating (unbalanced force)

Speed  To work out the speed of an object, we need to know two things:  The distance it has traveled  The time taken to travel that distance  The equation needed is Speed = Distance  To work out the speed of an object, we need to know two things:  The distance it has traveled  The time taken to travel that distance  The equation needed is Speed = Distance Time

Speed Formula Speed (s) Distance (d) Time (t) Speed = Distance  TimeTime = Distance  SpeedDistance = Speed x Time

Examples  Jack ran 100m in 12 seconds. What speed was he traveling at?  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different?  My car was going at 50mph for 1 hour. How many miles did I travel  My car was going at 50mph, and I traveled 20 miles. How long did this take me?  Jack ran 100m in 12 seconds. What speed was he traveling at?  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different?  My car was going at 50mph for 1 hour. How many miles did I travel  My car was going at 50mph, and I traveled 20 miles. How long did this take me? Speed Distance Time

Examples  Jack ran 100m in 12 seconds. What speed was he traveling at? Speed = 100  12 = 8.34m/s  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different? Speed = 100  15 = 6.67m/s (more air resistance)  My car was going at 50mph for 1 hour. How many miles did I travel Distance = 50 x 1 = 50 miles  My car was going at 50mph, and I traveled 20 miles. How long did this take me? Time = 20  50 = 0.4 hours (24 minutes)  Jack ran 100m in 12 seconds. What speed was he traveling at? Speed = 100  12 = 8.34m/s  Jack then ran 100m again, but this time it was much more windy, and it took him 15 seconds. What was his new speed, and why was this different? Speed = 100  15 = 6.67m/s (more air resistance)  My car was going at 50mph for 1 hour. How many miles did I travel Distance = 50 x 1 = 50 miles  My car was going at 50mph, and I traveled 20 miles. How long did this take me? Time = 20  50 = 0.4 hours (24 minutes) Speed Distance Time

Speed Experiment  Your task is to work out how your speed can vary - you are going to travel a distance of 20m by: -  Running  Walking  Skipping  Jumping  Backwards  You’ll need to time how long it takes you to cover this distance, so when we return we can work out your speed Speed = Distance  Time  Your task is to work out how your speed can vary - you are going to travel a distance of 20m by: -  Running  Walking  Skipping  Jumping  Backwards  You’ll need to time how long it takes you to cover this distance, so when we return we can work out your speed Speed = Distance  Time

Calculations