1. Dynamics and Space Velocity-time graphs

2. Learning Outcomes Velocity-time graphs for objects from recorded or experimental data. Interpretation of velocity time graph to describe the motion of an object. Displacement from a velocity time graph.

3. Lesson 1 Describe the motion of an object from a velocity-time graph. Draw a velocity-time graph from supplied data.

4. Velocity – Time Graphs We now know how to measure velocity at any given time. We can also use computers to record the velocity or acceleration second by second. These can be recorded on graphs called velocity-time graphs.

5. Velocity-Time Graphs

6. Increasing Velocity (same as constant acceleration)

7. Constant Velocity:

8. Decreasing Velocity (same as constant deceleration)

9. Drawing Velocity-time graphs Velocity always goes in the y-axis. Time is in the x-axis. Labels, units and 0 point should always be included.

10. Drawing Velocity-time graphs Task: Draw a v-t graph of the car described below. A car accelerates from rest to a velocity of 10 m/s in 4 s. It then remains at constant speed for a further 4 s before braking to a halt in another 2 s.

11. Lesson 2 Describe how to determine the displacement of a body from a velocity-time graph. Carry out calculations on the above.

12. Calculating Displacement from V-t Graphs Displacement (and distance) is related to the area under the v-t graph (shown here as A1, A2 and A3). NB: the biggest mistake pupils make here is using the equation d = vt THIS IS WRONG!!!

13. Areas: All areas under a v-t graph can be broken up into a series of triangles and/or rectangles: Area of a triangle = ½ lb Area of a rectangle = lb

14. Example Using the v-t graph below for the motion of a car find: a)Breaking distance. b)Total distance travelled. c)Average velocity. a)d = A3 = ½ lb = ½ (10)(10-8) = 10 m b)d = Areas A1 + A2 + A3 = ½ lb + lb + ½ lb = [½ x 10 x 4 ] +[10 x (8-4)] +[½ x 10 x (10-8) = 20 + 40 + 10 = 70 m c)V = d / t = 70 / 10 = 7 m/s

15. Summary Velocity-time graphs You should now be able to do the following: Draw velocity-time graphs for objects from experimental data. Interpret velocity-time graphs to describe the motion of an object. Calculate displacement from a velocity-time graph.