12. A car travels around a horizontal circular track of radius 45m.If the car increases its speed at a constant rate of 1.2m/s2 starting from rest, determine the time needed for it to reach an acceleration of 1.4m/s2. What is its speed at this instant?
13. The constant angular acceleration of a pulley is 4 rad/s2 and its angular speed its 3 rad/s. Determine the radius of the pulley if the total acceleration of a print on the rim of the pulley is 3.5m/s2.