Object in the Air

[greatwhiteshark]

An object is propelled vertically upward with an initial velocity of 20 meters per second. The distance s (in meters) of the object from the ground is s = -4.9t^2 + 20t.

a) When will the object be 20 meters above the ground?

b) When will it strike the ground?

c) Will the object reach the height of 100 meters?

d) What is the maximum height?

 

[wjm11]

An object is propelled vertically upward with an initial velocity of 20 meters per second. The distance s (in meters) of the object from the ground is s = -4.9t^2 + 20t.

a) When will the object be 20 meters above the ground?

b) When will it strike the ground?

c) Will the object reach the height of 100 meters?

d) What is the maximum height?

a) Set s = 20, solve for t.
b) Set s = 0, solve for t.
c) And d) This is the eqn of a parabola that opens downward. Therefore, the vertex represents the maximum height. Find the vertex.

 

[greatwhiteshark]

okay

Your steps are helpful, too.