7. An arrow was shot upward into the air. Five seconds later, the velocity of the arrow is 31.0 m/s downward, what is the initial velocity of the arrow? (Air resistance can be ignored.) A. 80.0 m/s, upward D. 18.0 m/s, downward B. 80.0 m/s, downward E. None of the above C. 18.0 m/s, upward 8. A car is traveling at a constant speed of 20.0 m/s when it is shifted into neutral. After traveling 30.0 m, the speed of the car reduces to 5.00 m/s. What is the acceleration of the car? A. -9.81 m/s2 D. -6.25 m/s2 B. -0.500 m/s2 E. None of the above. C. -2.00 m/s2 9. A baseball is thrown vertically into the air. The acceleration of the ball at its highest point is: A. zero B. 9.8 m/s2 up C. 9.8 m/s2 down D. changing suddenly from 9.8 m/s2 up to 9.8 m/s2 down E. cannot be calculated without knowing the initial velocity 10. A boat moves at 10.00 m/s relative to the water. If the boat is in a river where the current is 2.000 m/s, how long does it take the boat to make a complete round trip of 1.000 x 105 m upstream followed by a 1.000 x 103 m downstream? A. 200.0 s D. 204.1 s B. 208.3 s E. None of the above. C. 196.1 s2. Suppose A = B/C, where B has the dimension LZT-1, C has the dimension L-1M. The A has dimensions: A. LM /T B. 13 / TM D. L2 T / M C. TM / LZ E. M/LT 3. The angle between A = -25.01 - 45.0j and the positive x axis is: A. 29.0 D. 241 B. 61.0 E. 2990 C. 109 4. A delivery truck leaves a warehouse and travels 3.10 km south. The truck makes a right turn and travels 1.25 km west before making another right turn to travel 1.40 km north to arrive at its destination. What is the magnitude and direction of the truck's displacement from the warehouse? A. 2.11 km, 36.3 west of south D. 4.67 km, 15.50 east of south B. 4.67 km, 15.50 west of south E. None of the above C. 2.11 km, 36.3 east of south 5. A particle moves along x axis from x; to xf . Of the following values of the initial and final coordinates, which results in the displacement with the largest magnitude: A. Xi = 4m, xf = 6m D. xi = 4m, xf = -2m B. Xi = -4m, xf = -8m E. xi = 4m, xf = -4m C. xi = -4m, xf = 2m 6. A car travels 30 miles at an average speed of 60 mph and then travels 30 miles at an average speed of 30 mph. The average speed of the car for this 60 miles trip is: A. 35 mph D. 50 mph B. 53 mph E. 40 mph C. 45 mph