Using Kinematic Equations

Here is a question… A car initially travelling at 13 ms-1 rolls down a straight slope, accelerating at 0.6 ms-2 for 10 s. How far does the car travel in this time?

Five Variables, Five Equations vi vf d a t

Remember - kufss! known unknown formula substitute solve

Here is a question… A car initially travelling at 13 ms-1 rolls down a straight slope, accelerating at 0.6 ms-2 for 10 s. How far does the car travel in this time?

What are the “known” variables? Step One – “known” A car initially travelling at 13 ms-1 rolls down a straight slope, accelerating at 0.6 ms-2 for 10 s. How far does the car travel in this time? What are the “known” variables? vi = 13 ms-1 a = 0.6 ms-2 t = 10 s

d = ? (to be calculated) vf = x (not needed) Step Two – “unknown” A car initially travelling at 13 ms-1 rolls down a straight slope, accelerating at 0.6 ms-2 for 10 s. How far does the car travel in this time? What are the “unknown” variables? d = ? (to be calculated) vf = x (not needed)

Step Three – “formula” Which of the five formulae does not include vf (the one not needed) in it?

Step Four – “substitute” vi = 13 ms-1 a = 0.6 ms-2 t = 10 s

Step Five – “solve”

Here is another question… A windsurfer initially travelling at 3 ms-1 is accelerated by a strong wind gust, at 0.08 ms-2. What would be the windsurfer’s speed when he has travelled 100 m since the wind gust started? KUFSS – SHOW ALL WORKING

What are the “known” variables? Step One – “known” A windsurfer initially travelling at 3 ms-1 is accelerated by a strong wind gust, at 0.08 ms-2. What would be the windsurfer’s speed when he has travelled 100 m since the wind gust started? What are the “known” variables?

What are the “unknown” variables? Step Two – “unknown” A windsurfer initially travelling at 3 ms-1 is accelerated by a strong wind gust, at 0.08 ms-2. What would be the windsurfer’s speed when he has travelled 100 m since the wind gust started? What are the “unknown” variables?

Step Three – “formula” Which formula does not include the unneeded unknown variable?

Step Four – “substitute”

Step Five – “solve”

Try this now: What time does it take for an airplane to decelerate uniformly from 120 ms-1 to a stop if the distance covered along the runway is 1500 m?

Worksheet #5 (Q1, 2 and 3 only)