Two rocks are thrown horizontally at the same time and from the same height. if the initial speeds of rocks a and b are 10 m/s and 15 m/s, respectively, which statement below is true? you can ignore air friction a) rock a will hit the ground before rock b. b) rock b will hit the ground before rock a. c) rock a and rock b will hit the ground at the same time. d) the answer will depend on the masses of rock a and rock b

The horizontal speed has no effect on how long it flies before it hits the ground ... only how far it goes horizontally before it hits the ground.

Rock A and rock B will hit the ground at the same time. (C)  BUT ... Rock-B had more horizontal speed, so it'll go farther before it hits the ground.

Weirdly ... that means that if you aim a gun horizontally, and drop a bullet from the muzzle at exactly the same time as you shoot the gun, both bullets will hit the ground at the same time.  

i think it would be 80 km/h because 30 + 50 = 80 (sorry if this not the right answer i'm trying my best)

-4 on