A ball is thrown horizontally from a cliff at a speed of 10 m/s. Calculate its speed one second later (be sure to show your math steps)

The ball is thrown horizontally at 10 m/s.

Its horizontal speed doesn't change, but because of gravity,

it picks up vertical (downward) speed at the rate of 9.8 m/s

every second.

So at the end of one second, the ball is moving ...

horizontally at 10 m/s

and

downward at 9.8 m/s.

All together, it's moving in kind of a slanted direction,

at a speed of

√ (10² + 9.8²)

= √ (100 + 96.04)

= √ (196.04) = 14 m/s (rounded)