Question

1.A car goes off a cliff horizontally at 49 m/s and falls for 5 seconds

Answer 1

#1).  The horizontal speed doesn't change. 
The vertical speed is accelerated by gravity.

a).  Gravity increases the vertical speed by 9.8m/s every sec.
After 5 sec, the car is falling (5x9.8) = 49 m/s vertically.

b).  Horizontal:  49m/s !  Wow !  Almost 110 mph. No wonder he went off the cliff.
After 5 seconds, it's still 49 m/s.

c). After 5 sec, the horizontal speed and vertical-down speed are both 49 m/s.
The combination results in a velocity that points 45 degrees down from horizontal,
and its magnitude is

     square root of (49² + 49²) = 49 √2 = about 69.3 m/s .