Kinematics (Part 2)

Solving Kinematics Problems 3 very important Equations… Get Your equation sheet

Average Velocity Vector Quantity Could have a negative value Change in position divided by change in time Δ = delta  “change in” v = Δ d (df – di) “f” = final or end Δ t (tf – ti) “i” = initial Units are things like (mi/hr, km/hr, m/s)

Distance Scalar Quantity Simple manipulation of previous equation Δ D = v x Δ t Units are things like (m, km, mi)

Average Acceleration Vector Quantity Change in velocity divided by change in time a = Δ v (vf – vi) Δ t (tf – ti) Units are m/s2

Solving Kinematics Problems Use the guess Method

GUESS Method A systematic way to not only set up the problem, but also solve the problem and get the correct answer. “G” – write down what is given “U” – write down the unknown “E” – write down the equation to be used “S” – substitute values into equation “S” – solve the problem

Example Problem #1 How long will it take to travel 50.0 miles in a car traveling at 65 mi/hr? d= 50.0 miles v= 65 mi/hr t=?s Δd = v x t so… t = Δd/v t= (50.0mi)/(65mi/hr) t= 0.77 hr

Example Problem #2 A car is traveling at 18.5 m/s. The driver steps on the gas to pass a garbage truck. After 5.0 seconds, the car is traveling at 24.5 m/s. What is the car’s rate of acceleration? vi = 18.5 m/s vf = 24.5 m/s t = 5.0 s a = ??? a = Δv / Δt a = (24.5 m/s – 18.5 m/s) (5.0 sec) a = 1.2 m/s2