1. Year 10 Physical World Motion

2. Objectives Measure distance. Measure time. Calculate speed of objects using v = d / t Know the terms kinetic energy and gravitational potential energy. Know the SI units for distance, speed and time ( + km, cm and mm) Graph distance versus time for constant speeds. Describe motion from distance/ time and speed / time graphs.

3. SI units mm = milimetres cm = centimetres m = metres km = kilometres s = seconds min = minutes h = hours ms -1 = metres per second kmh -1 = kilmetres per hour

4. Units of distance (d) What do the following units stand for?? mm? cm? m? km? a) How many mm in 1cm? b) How many cm in 1m? c) How many m in 1km? d) How many cm in 1km? e) How many mm in one m?

5. Units of time (t) What do the following units stand for?? s? min? h? a)How many ‘s’ in 1min? b)How many min in 1h? c)How many ‘s’ in 1h?

6. Calculating speed When objects move a distance we can time them moving. Using the two values we can work out speed by using the equation below. v

7. Speed triangle To remember the equation you can use this triangle. Each part of the equation is put into the different parts of the triangle. You then cover the value you want to find. For example if you know distance and speed. Cover time, the thing we don't know, and you see the equation that you need d ÷ v =t. v

8. Energy Kinetic energy – any object that is moving has kinetic energy. Gravitational potential energy – when an object is lifted it has gravitational potential energy. E.g. a child at the top of a slide has gravitational potential energy, as it slides down the slide it gains kinetic energy but loses its gravitational potential energy

9. Distance time graphs The slope of the graph represents the speed of the object. A straight line represents a constant speed A horizontal line shows a zero speed, the object is not moving. The steeper the slope, the greater the speed.

10. If something is not moving, a horizontal line is drawn on a distance-time graph (dt-graph). Time is increasing to the right, but the distance does not change. The object is stationary. Stationary on a Distance-Time graph

11. If something is moving at a steady speed, it means we expect the same increase in distance in a given time: Time is increasing to the right, and distance is inceasing steadily with time. The object is moving at a steady speed. Steady speed on a Distance-Time graph

12. The line below is curving upwards. This shows an increase in speed, since the gradient is getting steeper: In other words, in a given time, the distance the object moves is larger. It is accelerating Acceleration on a Distance-Time graph

13. - Moving at a steady speed, slowly - Not moving for quite some time - Moving again, but at higher speed Analysing a journey on a Distance-Time graph

14. Look at the following graph. The fastest motion is shown by the yellow line. speed = distance / time so the steeper the line the faster the speed Yellow: speed = distance / time = 30 m / 10 s = 3 ms -1 Blue: speed = distance / time = 20 m / 20 s = 1 ms -1 Comparing 2 lines

15. D-T and V-T graphs The first thing to note about these is that, on first glance, they look EXACTLY the same as distance time graphs!distance time graphs The only way you can tell the difference is by reading the labels on the axes.

16. Constant speed on a ‘Speed-Time’ graph On the graph below the speed is constant and time is passing. The object is NOT stationary!

17. Acceleration on a ‘Speed-Time’ graph When the speed is increasing as time is passing, the object must be accelerating.

18. Deceleration on a ‘Speed-Time’ graph When speed is falling as time is passing the object must be decelerating (slowing down).

19. Comparing 2 lines on a speed-time graph Both the yellow and blue line show increasing speed. They both reach the same top speed, but the blue one takes longer. What is the difference? The yellow line shows a greater acceleration.

20. Calculating distance using a Speed-Time graph Speed-Time graphs can be used to find out how far something has travelled. In the example below, a speed of 30 m/s is maintained for 20 seconds: One way of calculating the distance is to use distance = speed × time. This gives: distance = 30 × 20 = 600 m

21. Calculating the area under the line in a speed-time graph An alternative way of finding the distance travelled is simply to calculate the area under the line: In this case: distance = 30 × 20 = 600 m. Which is precisely the same calculation as before!