Question

With what initial velocity must an object be thrown upwards so that it will reach a maximum height of 800 feet? Assume the that the object experiences an acceleration of a (t) = −32 ft / sec2 due to gravity. Assume no air friction or other forces working on the object.

a) 7.07 ft/sec
b) 226 ft/sec
c) 131 ft/sec
d) 51,200 ft/sec

Answer 1

Option b is right.

Explanation:

When an object is thrown upwards, the acceleration acting is acceleration due to gravity in a negative manner.

a = -32 ft/sec square

Initial velocity let it be u

Final velocity when it reaches maximum height is 0

Use the formula connecting, u, v, a and s

`v^2=u^2+2as\\0 = u^2-2(32)(800)\\u = √(64(800)) \\u = 160*0.707\\= 226.27`ft/sec

Hence we find that initial velocity is 226 ft/sec

Option b is right.