solving an olympic word problem!(velocity in parabola...)

[han924]

This is the problem I'm having great trouble on,,

y=-0.5gt² + v₀tsinΘ + y0

(this is the equation to find the high jumper's trajectory)

y=the height of the jumper(meters)

g=acceleration due to gravity (-9.8 m/s²)

t= time (seconds)

v₀= initial velocity of the jumper (m/s)

Θ = launch angle from horizontal (degrees)

y₀= initial height (meters) (assuming the jumper starts from the ground, this will be zero.)

question:
If the average running speed of a high jumper is 10m/s and the average launch angle is 42

degrees, find the time the jumper is in the air while clearing a 2m jump. ----------------------------------------------------------------------------------------
I'm having great trouble with this question, so please help me..! I have no idea how to find the time...:-(

 

[Deleted member 4993]

This is the problem I'm having great trouble on,,

y=-0.5gt² + v₀tsinΘ + y0

(this is the equation to find the high jumper's trajectory)

y=the height of the jumper(meters)

g=acceleration due to gravity (-9.8 m/s²)

t= time (seconds)

v₀= initial velocity of the jumper (m/s)

Θ = launch angle from horizontal (degrees)

y₀= initial height (meters) (assuming the jumper starts from the ground, this will be zero.)

question:
If the average running speed of a high jumper is 10m/s and the average launch angle is 42

degrees, find the time the jumper is in the air while clearing a 2m jump. ----------------------------------------------------------------------------------------
I'm having great trouble with this question, so please help me..! I have no idea how to find the time...:-(

I'll start you off: assume g = 9.8 m/s²

then you have

2 = -4.9 * t² + 10 * sin (42°) * t + 0

solve for 't'

Please share your work with us, indicating exactly where you are stuck - so that we may know where we can begin to help you.

 

[Deleted member 4993]

Above is a Quadratic Formula.

Do you know how to solve those?

If not, for a quick review, go to:

http://www.purplemath.com/modules/quadform.htm

If you have further question - come back here and ask (showing what you have tried).