Plz, Can someone explain the rest of this problem in a way that I mite understand it... THNX!?

Question

- A ball is projected horizontally from the edge of a table that is 1.00 m high, and it strikes the floor at a point 1.20 m from the base of the table. (a) What is the initial speed of the ball?(b) How high is the ball above the floor when it's velocity vector makes a 45 degree angle w/ the horizontal.

Ok. For (a).. I found the time to be .45 sec and used that to find the initial velocity which i found to be 2.67 m/s...
(b) is rlly confusing me... I don't get it at all... The angle is confusing me... I drew the projectile but ... SOMEONE HELP!

Answer 1

first thing u should do is do draw the path of the projectile, using only imagination, the ball will definetly fall down as it moves away from the table edge until it finally hits the floor.

projectile path is always parabolic, and the direction of the velocity vector is tangent to the path of the projectile at any point.

at the initial state, the velocity vector was pointing left or right according to your assumption, but as the parabolic path falls down, the velocity vector points down with it, when the ball hits the floor the velocity vector will be perpendicular to the horizontal in the downward direction.

so at 45 degrees downward, the velocity vector has two components, on in the horizontal V*cos(theta) and another downward V*sin(theta), to get how high the ball at this instant apply the same laws but use V*sin(theta) instead of V , and to find how far from the table use V*cos(theta) instead of V.

hope this helped.

Answer 2

If my memory is accurate, the velocity vector would be 45 deg from horizontal when the horizontal and vertical velocity are equal. According to your question you have calculated the horizontal velocity. If you know how to calculate the vertical speed and distance, solve for the time when vertical speed = horizontal speed. Finally, solve for distance above ground at that time.

I hope this helps. Physics was half my lifetime ago.