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Motion- Speed and Velocity Speed,Distance and Time Speed is the the rate at which someone or something is able to move or operate. To calculate speed you divide the distance by time taken. If the time was measured in seconds (s) and the distance in meters (meters) the speed will be written in m/s. Speed,Distance and Time A car travels a distance of 300 km in 3 hours. What’s is the car’s speed? Distance: 300 Time: 3 = 100 km/h Speed, Distance and Time But what if this was the question? A car travels at a speed of 100 km/h for 3 hours, how far did the car go? or How long would it take a car to travel 300 km at a speed of 100 km/h ? Speed, Distance and Time Then we’d have to use the Speed Triangle. Converting Units To convert m/s to km/h Distance covered in 1 sec =1m distance covered in 3600s= 3600m i.e. In 1 hr =3.6km covered I.e. 1m/s =3.6 km/h To convert km/h to m/s Distance covered in 1hr =1km 1hr =3600 seconds I.e. Distance covered in 3600 sec = 1000 m Distance covered in 1 sec = 1000/ 3600 m I.e.1 km/hr =0,2777… m/s 1.Convert 10 km/h to m/s 2. Alex drives 30 km for 15 minutes. What is his speed in km/h? 3. Sally walks 3000 meters in 900 seconds what is her average speed in km/h Speed and Velocity Speed is the the rate at which someone or something is able to move or operate. Velocity is the speed of an object or someone at a certain direction ● For example: Kate walked at a speed of 6 m/s going north she then turned east and walked at a speed of 6.8 m/s Acceleration Acceleration: the rate at which an object changes its velocity. Acceleration = Change in Velocity ➗ Time Taken Acceleration A bike starts from rest and accelerates to 20 m/s over a period of 6 seconds. What is the acceleration of the car? Acceleration A car’s acceleration is 20 m/s2 it accelerates for 20 seconds. What is the change of velocity? Acceleration A car decelerates from 20m/s to 60m/s at a rate of 5 m/s2. How long does this acceleration take the car? Distance/Time Graph Distance/Time Graph Distance: 10-40 30m Time: 40-60 20 s 30/20= 1.5 m/s The slope of a distance time graph tells us the speed. We can tell which object is going faster by the graph’s slope, if objects travelled the same amount of distance. Which one is faster? Speed/Time graphs Constant Acceleration Constant Speed Constant Deceleration Speed/Time Graph 60 50 20/2= 10 Change in Speed: 0-20 --> 20 Time taken: 0-2 2hr 10 k/h2 40 30 20 10 0 1 2 3 4 5 6 Speed/Time graphs To calculate the distance you calculate the area under the graph 60 50 40 30 20 10 0 1 2 3 4 5 6