Answer: 80mph describe the speed of your brother
Acceleration (magnitude anyway) = (change in speed) / (time for the change) .
Change in speed = (10 - 30) = -20 m/s
Time for the change = 4.0sec
Magnitude of acceleration = -20/4 = <em>-5 m/s² </em>
Answer:
A) False
B) False
C) True
D) True
E) True
Explanation:
A) The formula for tangential speed v in term of angular speed ω and radius of rotation r is

So if the angular speed is constant and 0, the tangential speed is also 0. A) is false
B) False because of the centripetal acceleration:

C) True because of the formula for tangential acceleration in term of angular acceleration α is

D) True because same as D), if it has angular acceleration, it would have a tangential acceleration. Also from B) the centripetal acceleration will come with time as soon as angular speed is generated by angular acceleration.
E) True and same explanation as from B)