1. Nov 28, 2008

### cbrowne

1. The problem statement, all variables and given/known data

A man standing on the sidewalk throws a set of keys vertically upward to his
wife in the window of their apartment 4.0 m above. The wife catches the keys
1.5 s later. (a) With what initial speed were the keys thrown? (b) What is the
velocity of the keys just before they were caught? (c) Draw a diagram showing
the trajectory of the keys.

2. Relevant equations

3. The attempt at a solution

d= 4.0 m
Δt= 1.5 s
g= -9.8 m/s^2

Δd= ViΔt+1/2aΔt

-ViΔt= 1/2 at2-Δd

-Vi= 1/2 at2- Δd /Δt

-Vi= -10.016 m/s

ANSWER FOR 7-A ->>Vi= 10.016 m/s

Vf= 4.68333 m/s

2. Nov 29, 2008

### alphysicist

Hi cbrowne,

I don't believe that equation will answer the question. It gives the speed, but they are asking for the velocity.

When you use the equation:

$$V_f = \pm 4.68333 \mbox{ m/s}$$