Problem: A car is moving at 30 mph as it enters a circular curve of radius 700 ft. When it exits the curve 8 seconds later, it has changed direction by 90^o and has speeded up uniformly to 45 mph. Find:

a) the tangential acceleration
b) the radial acceleration at the exit point
c) the total acceleration at the exit point (assuming it's still accelerating)

Since this value is exact (the 5280 ft/mi is a definition, and so is the 3600 s/hr), we use this value to make the second conversion:

a) The tangential acceleration is the same throughout the motion...

b) The radial acceleration depends on the tangential velocity and changes with time...

c) The total acceleration is the vector sum of the two accelerations above. Since they are perpendicular,

Here's a picture to help you visualize this: