# Homework Help: Help Plzzz

1. Mar 14, 2005

### krypto

Projectile Problem With Athelete

This is the question:
An athlete executing a long jump leaves the ground at a 35° angle and travels 5.80 m.
a) What was the takeoff speed?
b) If this speed were increased by just 5.0 percent, how much longer would the jump be?

ive worked out the initial velocity = speed x sin 35 (is that rite)
i know it has somethin to do with the angle and sin but im not sure how to put it onto an equation :S i keep getting 3.32 but its not rite :(
wat am i doin wrong?

Last edited: Mar 14, 2005
2. Mar 14, 2005

### sevens

Velocity as a vector or as its components?

well from what you state in the problem you know that
X inital is 0
X final is 5.8 m and
V final is 0.
a is the acceleration of gravity

if you just want to find the take off velocity you would use

$$(Vfinal)^2 = (Vinitial)^2 + 2a(Xfinal - Xinitial)$$

this gives you velocity as a vector if you want to break it down into x and y components then you would do

$$(Vinitial)*sin(theta)$$
for the y dirrection

and

$$(Vinitial)*cos(theta)$$
for the x dirrection