Physics
posted by Darrell .
A football player throws a ball with a horizontal distance of 31.0 m so that the other player catches it at the exact height it was initially thrown. If the ball rises and falls by 1.8 m in its trajectory, what is the initial velocity of the ball? Please give the speed and angle!

how much initial speed up, Vi, to go up 1.8 m?
m g h = (1/2)m Vi^2
Vi^2 = 2 g h
Vi^2 = 2 (9.81)(1.8)
Vi = 5.94 m/s vertical component
Now work on horizontal problem
average speed up =5.94/2 = 2.97 m/s
so time rising up = 1.8/2.97 =.606 s
it goes distance 31/2 = 15.5 m while rising
so u, the constant horizontal component of velocity = 15.5/.06 = 25.6 m/s
so in the end tinital velocity is u = 25.6 and v = 5.94
speed = sqrt(u^2+Vi^2) = 26.3 m/s
tan elevation angle = 5.94/25.6
so angle = 13.1 degrees up from horizontal
Respond to this Question
Similar Questions

physics projectile motion
A player passes a basketball to another player who catches it at the same level from which it was thrown. The initial speed of the ball is 7.1 m/s, and it travels a distance of 4.6 m. What was (a) the initial direction of the ball … 
Math
We are studying Quadratic formula: A football player punts a ball. The path of the ball can be modeled by the equation y=0.004x(squared) + x + 2.5, where x is the horizontal distance, in feet, the ball travels and y is the height, … 
math
Please explain in detail so I can understand how to do it: A football player punts a ball. The path of the ball can be modeled by the equation y = 0.004x^2 + x +2.5, where x is the horizontal distance, in feet, the ball travels and … 
physics
A basketball of mass 0.602 kg is passed to a player of mass 83.0 kg who jumps off the floor while catching the ball. The player's center of mass is instantaneously at rest just before he catches the ball, which is initially moving … 
physics
A 70.5kg football player is gliding across very smooth ice at 2.05m/s . He throws a 0.470kg football straight forward. What is the player's speed afterward if the ball is thrown at 14.5m/s relative to the ground? 
physics
A football is thrown from the edge of a cliff from a height of 22 m at a velocity of 18 m/s [39degrees above the horizontal]. A player at the bottom of the cliff is 12 m away from the base of the cliff and runs at a maximum speed of … 
Physics
A 69.5kg football player is gliding across very smooth ice at 2.15m/s . He throws a 0.470kg football straight forward. What is the player's speed afterward if the ball is thrown at 16.0m/s relative to the ground? 
Physics
A 69.5kg football player is gliding across very smooth ice at 2.15m/s . He throws a 0.470kg football straight forward. A) What is the player's speed afterward if the ball is thrown at 16.0m/s relative to the ground? 
Physics
A 69.5kg football player is gliding across very smooth ice at 2.15m/s . He throws a 0.470kg football straight forward. A) What is the player's speed afterward if the ball is thrown at 16.0m/s relative to the ground? 
Physics
A football player kicks a ball of mass 1.534 kg across the field using a constant force of 13.4 N over a distance 30.0 m. How much work does the football player do?