1. Problem 4

Aballwasthrownverticallydownwithaninitialspeedvi(B)ontothehard ground below.It hit

the surface after time t at the contact speed vc(B) and bouncedstraight back at the same speed. It

then moved vertically up and caught back at the same height with afinal speed vf(B) at time 2t

afterbeing throwndown. Ignorethe effectsfrom airon theball.

1. Draw the velocity vs. time graph for the entire motion of the balland mark the given

information on the graph. Use "upward direction positive" signconvention.

1. Using the properties of the velocity vs. time graphs alone,determine the relationship between

vi(B) and vf(B).1

1. Problem 5

Acarthatismovingalongahorizontalstretchofacityroadtakes120 s to move between two

trafficlightswhicha2145mapart.Thecarstartedfromrestatthefirsttraffic lights and increased

its speed at a constant rate for 30 s until in reached a 22 m/s speed.

After moving at this speed

forTsecondsthecarsloweddontosmoothlystopatthesecondtrafficlight.Amotorcyclist who

leftthefirsttrafficlights10safterthecarincreaseditsspeedataconstant rate and passed the

carafter990mfromthefirsttrafficlights.Whenthemotorcyclistpassed it, the car had already

begun to move at the constant speed.

1. Draw velocity verses time graphs for the car and the motorcyclein the same plot (use the

graphs to answer the next few questions)

1. Howlongdidittaketothemotorcyclisttopassthecar,afterstartingfrom the first traffic

lights?

1. What was the acceleration of the motorcyclist?
2. How long did the car moved at the constant speed of 22 m/sbefore starting to slow down?