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 Youll 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 Youll 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