(9) A projectile is fired with a initial speed of 75.2 m/s at an angle of 34.5^o above the hotizontal on a long flat firing range. Determine (a) the maximum height reached by the projectile, (b) the total time in the air, (c) the total horizontal distance covered(that is, the range), (Ans. 539m)and (d) the velocity of the projectile 1.50s after firing. (11) A 400-kg ice-boat moves on runners on essentially frictionless ice. A steady wind blows, applying a constant force to the sail. At the end of an 8.0-s run, the acceleration is 0.50m/s^2. (a)What was the acceleration at the beginning of run? (b)What was the force due to the wind? (13) An 59-kg woman stands in an elevator. What force does she exert on the floor of the elevator under the following conditions? (a) The elevator rises with a constant velocity of 2.0 m/s. (c)The elevator goes down with a constant velocity of 4.0 m/s. (e) While going down, the elevator decelerates at 1.5 m/s^2. I want to ask that what is the diff. between x=xo+1/2(vo+v)t and s=1/2(u+v)t. what is the meaning of xo and x? And which equ will given during the exam?