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I have a few question i don't understand how to complete.

## Homework Statement

A model rocket leaves the ground, heading straight up at 49m/s.

a)What is the maximum altitude?What are its speed and altitude at b)1s c)4s

**2. Homework Equations ( For all questions)**

Constant acceleration formulas

Average speed equation

## The Attempt at a Solution

Question a) i understand how to complete, however how would i solve b)

This is what i have tried:

t=1s

v-final=?

v-initial=0

a=9.80

used the v-final=v-initial + at

v-final = 9.8m/s

this is incorrect what have i done wrong?

## Homework Statement

A jetliner leaves San Francisco for New York, 4600km away. With a strong tailwind, its speed is 110km/h. At the same time, a second jet leaves New York for San Francisco. Flying into the wind, it makes only 700km/h. When and where do the two planes pass each other?

## The Attempt at a Solution

Well firstly i tried to find the time from NY to SF and NY to SF.

So i get 4.18hrs and 6.57hrs. I minus the figures to get the time that the two planes pass which is 2.37hrs. However according to the book's answer this is incorrect.

For the distance i went 400(1100-700) * 2.39 = 956km.

## Homework Statement

A hockey puck moving at 32m/s slams through a wall of snow 35cm thick. It emerges moving at 18m/s. a) How much time does it spend in the snow? b) How thick a wall of snow would be needed to stop the puck entirely.

## The Attempt at a Solution

i found question a) was t=0.014s, but could not find the correct answer to question b)

I have tried doing the following:

[tex]x= \frac{v-initial - v-final}{2} * t[/tex]

[tex]x=\frac{32}{2} * 0.014[/tex]

x=0.224m

P.S