#1 (permalink)

two stones A and B are thrown horizontally fom the top of the cliff. stone A has an initial speed of 15 meters per second and stone B has an initial speed of 30 meters per second. compared to the time it takes stone A to reach the ground, the time it takes stone B to reach the ground is?

1) the same
2) twice as great
3) half as great
4) four times as great

some help would be nice im stuck

#2 (permalink)

they would be the same.

Why?

It says the rocks are thrown off of the cliff with horizontal speed. If you discount air resistance, horizontal speed will always remain the same. Also, horizontal speed will not affect vertical speed at all, and if you payed attention in class, you know that objects accelerate 9.8 meters per second per second vertically because of gravity. This includes all objects. Because both objects in this example had an initial vertical speed of zero, and they will be accelerating at the same rate, they will always have the same speed downwards. Thus, they will impact the ground at the same time.

Try it! Take two paper wads, and flick one horizontally off of a rail while dropping the other simultaneously. If done correctly, they will impact the ground at the same time!

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#3 (permalink)

oh thx for the help =)