Interpreting date: bob straps on his
in-lineskatesand pushes down a hill. his velocity changes from 0
m/s atthe start to 4.5 m/s exactly 15 s later: what is bob's
averageacceleration?

is Bob's  average acceleration.

Explanation:

Initial velocity of the bob's in-lineskates= u = 0 m/s

Acceleration of the Bob= a  = ?

Final velocity of the bob's in-lineskates= v = 4.5 m/s

Duration of time in which 0 m/s velocity is changed to 4.5 m/s = t = 15 s

Using first equation of motion: v = u + at

is Bob's  average acceleration.

the scientific method.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.