A train starting from rest accelerates at 4 m s-2 ?
Density, Speed and Acceleration 28 for 5 s. Calculate its velocity at the end
Density and Motion
of the 5 s. A car starts from rest with a constant acceleration of 6 m s-2 a speed of 30 m s-1
. How long will it take to reach
Thinking and Investigating 1. The table shows the distances travelled at different times by a boy running.
Time (s) Distance (m)
0 0
1 4
2 8
3 12 4 16 5 20
(a) Graph the results, putting time on the horizontal (x) axis. (b) Use the graph to find: (i) The time taken to run 10 m. (ii) The distance travelled in 5.5 seconds. (iii) The speed of the runner.
(c) What does the shape of the graph tell you about the relationship between time and the distance the boy has run?
(d) Sketch a similar graph to represent the boy gradually slowing down as he runs. (e) Sketch a similar graph to represent the boy gradually speeding up as he runs.
2. Use Google maps to find out how far you travel to school each morning. Record how long your journey takes. (a) What exactly can these two pieces of data be used to calculate? (b) Plot a Distance versus Time graph of your typical journey to school . Think about how any stops in your journey will be represented on the graph.
3. This table shows the velocity of a car at different times. Time (s)
Velocity (m s-1 )
0 0
1 5
2 10 3 15 6 24 7 28 8 32
4 20
(a) Graph the results, putting time on the horizontal (x) axis. (b) Use the graph to find: (i) The velocity at 3.5 seconds. (ii) The time at which the velocity is 8 m s-1 (iii) The time taken to change from 4 m s-1
. to 14 m s-1 .
(c) Is the velocity unchanging (steady)? (d) Is the car accelerating? (e) If the car is accelerating is the acceleration constant? (f) Draw a similar graph to represent the car accelerating for 10 seconds, then keeping a constant velocity for 10 seconds and finally decelerating to a stop in 5 seconds.
