- #1

wheels94

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## Homework Statement

A kicker wishes to kick a field goal, so he sets the ball on the ground 30 yards (27m) from the goal. Assuming he kicks the ball at an angle of 45 degrees and a speed of 27m/s, what is the height of the ball above the ground when it goes over the crossbar.

**Known:**

R = 27m

Vo = 27ms

theta = 45

**Unknown:**

t:

Vox:

Voy:

Sy:

## Homework Equations

Vox = Vo *cos(theta)

Voy = Vo *sin(theta)

R = Vox*t

Sy = Voy*t+.5*a*(t)^2

## The Attempt at a Solution

**Step 1: Find**

*Vox:*Vox = Vo *cos(theta)

Vox = 27 *cos(45)

Vox = 19.1m/s

**Step 2: Find**

*t*:R = Vox*t

27 = 19.1*t

t = 27/19.1

t = 1.4s

**Step 3: Find**

*Voy*:Voy = Vo *sin(theta)

Voy = 27 *sin(45)

Voy = 19.1m/s

**Step 4: Find**

*Sy:*Sy = Voy*t+.5*a*(t)^2

Sy = 19.1*1.4 + .5(-9.8)(1.4)^2

Sy = 26.7-9.6

Sy = 17.1m

However, this is not the answer in the back of this book (Practice Makes Perfect Physics by Connie J Wells). The answers given are t=1.4s and h (which I've so far assumed is Sy)= 17.7m

I've only recently started brushing up on my physics over the last year as prep for University, so I'm fully expecting there to be an error here somewhere, but I've already come across one error in this book, is this possibly another one?