Physics Help!?

NEED 2 B) Pre Lab for Physics.... need help due tom.... should be easy for physics people?

• Physics Lab 2: UNIFORM ACCELERATED MOTION IN 1 D Pre-Lab Exercises 2. A physics student throws a ball from the top of the Physics Bldg, vertically up with an initial velocity of 10 m/s. At the same moment, another student throws a ball from the ground level, vertically up, with an initial velocity of 20 m/s. The height of the Physics Bldg is 20 m. a) Find the time at which the two balls pass each other. i got 2 seconds b) Find the height with respect to the ground at which they pass each other. Which way is the first ball moving when they pass each other? i don;t know how to do this one

• Answer:

  I'm going to accept your 2 second figure because I am too lazy to recalculate it. As for part b, you have expressions y1(t) and y2(t) for the height of each ball; equate these and solve for t and that will give the time at which they pass each other. Substitute this back into either to get the height. Differentiate both expressions with respect to time and set the derivatives to zero to get equations for the time of maximum height of each, and compare the times just obtained with the time of meeting to see whether the meet happens before or after each ball reaches its maximum height.