GIVEN INFORMATION:
A car enters a straight highway at 15.0 mph and starts picking up speed at a rate of 4.50 m/s^2 until it moves at 65.0 mph.
QUESTIONS:
1. How long does it take and how much distance (in meters) does the car travel?
2. At what rate should you slow down to stop in 100 feet, if your initial speed is 80.0 mph?
Thank you very much for your time. Explain how you got your answers if you can! ^^
A car enters a straight highway at 15.0 mph and starts picking up speed at a rate of 4.50 m/s^2 until it moves at 65.0 mph.
QUESTIONS:
1. How long does it take and how much distance (in meters) does the car travel?
2. At what rate should you slow down to stop in 100 feet, if your initial speed is 80.0 mph?
Thank you very much for your time. Explain how you got your answers if you can! ^^
-
1
V(t) = Vi + a*t => 65 = 15 + 4.5*t => t = (65-15)/4.5 = 11.1s <-------- 1
distance = Vi*t + 1/2 *a*t^2 = 15*11.1 + 0.5*4.5*11.1^2 = 444.4m <-------- 1
2
Convert 80mph to m/s
80mi/hr *5280ft/mi * 1hr/3600s *0.3048m/ft = 35.8m/s
Vf^2 = Vi^2 + 2*a*d
0 = 35.8^2 + 2*a*100*0.3048 => a = 35.8^2/60.96 = -21m/s^2 <------ 2
Negative because it is deceleration
V(t) = Vi + a*t => 65 = 15 + 4.5*t => t = (65-15)/4.5 = 11.1s <-------- 1
distance = Vi*t + 1/2 *a*t^2 = 15*11.1 + 0.5*4.5*11.1^2 = 444.4m <-------- 1
2
Convert 80mph to m/s
80mi/hr *5280ft/mi * 1hr/3600s *0.3048m/ft = 35.8m/s
Vf^2 = Vi^2 + 2*a*d
0 = 35.8^2 + 2*a*100*0.3048 => a = 35.8^2/60.96 = -21m/s^2 <------ 2
Negative because it is deceleration