Solving Word Problems Using Kinematics Equations

Example Problem A fan cart takes 7.5 seconds to travel 4.0m from a standing start. How long will it take this same car to travel 6.0m, again from a standing start?

Equations Duration  t = t f – t i Displacement  x = x f –x i Avg Speed S avg = d /  t Avg Velocity v avg =  x/  t Avg Acceleration a avg =  v/  t

Kinematics Equations For Constant Acceleration  x = v i t + ½ at 2 v f = v i + at  x = ½(v i + v f )t V f 2 = v i 2 + 2a  x

Terms – Definitions -time- -duration- -position- -distance- -displacement- -speed- -velocity- -acceleration- Which of these terms relates two other terms?

Ex. From a stand-still, a train can cover 100m in 20 seconds. – What is the train’s acceleration? (assume it is constant) – With the same constant acceleration, how long would it take the train to complete 400m (a quarter mile) from a standing start?

Ex In the automotive industry, a 0.5g panic stop is the name for a situation when a driver slows the vehicle by ½ the acceleration due to gravity. That means the car is slowed by 4.9m/s/s. How far will it take a driver to execute a 0.5g panic stop from: – 25 mph? – 50 mph?

Motion With Constant Acceleration Part 2 1.a) a = 2m/s/s b) a = 4m/s/s 2. a = 0.4m/s/s 3.a) a = 3m/s/s b) a = 3m/s/s c) a = 3m/s/s 4.Invalid question! 5.Invalid Question!  t = 1.02s

Motion With Constant Acceleration Part 3 1.a) a=2m/s/s b) a=2m/s/s 2.a=-1.6m/s/s 3.a) a=-3.5m/s/s b)  x = 63m c)  x = 252m 4.v f = 56.4m/s 5.a = -5m/s/s OR 5m/s/s west 6.a) a = -6.67m/s/s b) S avg =20m/s c) t = 1.5s