Your name is Galileo Galilei and you toss a weight upward at 8 feet per second from the top of the Leaning Tower of Pisa (height 185 ft).
(a) Neglecting air resistance, find the weight's velocity as a function of time t.
v(t) = ? ft/s
(b) Find the height (in feet) of the weight above the ground as a function of time.
s(t) = ?
Where and when will it reach its zenith?
? ft
? s

a) [ft/s]

b) [ft]

c) 186 ft at 0.248 s

Explanation:

a)

The motion of the weight is a free fall motion, which is subjected only to the force of gravity, downward.

Therefore, the motion of the object will be a uniformly accelerated motion, with constant acceleration of

(acceleration due to gravity)

in the downward direction.

Therefore, the velocity of the weight after time t will be given by the following suvat equation:

where:

is the initial vertical velocity (upward)

t is the time

Substituting the values of u and g, we find

[ft/s]

b)

Since the motion of the weight is a uniformly accelerated motion, the expression that gives the displacement of the object at time t (and therefore, its height at time t), is given by

where

is the initial height of the weight

is the initial vertical velocity (upward)

(acceleration due to gravity)

t is the time

And substituting these values, we find:

[ft]

c)

The time at which the weight reaches its maximum height above the ground can be found from the equation of the velocity: in fact, at the moment of maximum height, the direction of the weight changes, so its velocity will be zero at that instant:

So we have

And solving for t,

So, the weight reaches its maximum height after 0.248 s.

In order to find the maximum height, we just need to substitute this time into the equation of the height, h(t).

By doing so, we find:

the diagram which shows forces as either balanced = same speed or unbalanced = accelerarting

d is the correct answer