Achild throws a baseball upward with an initial velocity of 20 m/s. the child wants to throw the baseball at least as high as the very top of the 20 m tall tree in his backyard. (assume g = 9.80 m/s2 and no air resistance) answers : we need more information no yes

When the ball starts its motion from the ground, its potential energy is zero, so all its mechanical energy is kinetic energy of the motion:

where m is the ball's mass and v its initial velocity, 20 m/s.

When the ball reaches its maximum height, h, its velocity is zero, so its mechanical energy is just gravitational potential energy:


for the law of conservation of energy, the initial mechanical energy must be equal to the final mechanical energy, so we have

From which we find the maximum height of the ball:


Therefore, the answer is yes, the ball will reach the top of the tree.