<span>When an object moves in a circle, the acceleration points toward the center of the circle. This acceleration is called centripetal acceleration.
We can use a simple equation to find centripetal acceleration.
a = v^2 / r
We can use this same equation to find the speed of the car.
v^2 = a * r
v = sqrt { a * r }
v = sqrt{ (1.50)(9.80 m/s^2)(11.0 m) }
v = 12.7 m/s
The speed of the roller coaster is 12.7 m/s</span>
They can't hear an echo in small room because in it the sound can't be reflected back. For an echo of a sound to be heard,the minimum distance between the source of sound and the walls of the roomshould be 17.2 m. Obviously,in asmall room echoes cannot beheard.
One reason that it would be appropriate to talk on your cell phone, could be reporting an accident. For instance, a car crash, a sign in the road anything regarding safety of drivers.
