How do i account for the height for projectile motion

[rashad764]

Homework Statement

A child throws a ball with an initial speed of 8.00 m/s at an angle of 40.0° above the horizontal. The ball leaves her hand 1.00 m above the ground and experience negligible air resistance.

(a) How far from where the child is standing does the ball hit the ground?
(b) How long is the ball in flight before it hits the ground?

Homework Equations

R(θ) = v₀^2(sin(2θ))/g for a
2v₀(sinθ)/g for b

The Attempt at a Solution

the above formulas assume that the object is at ground level, however the question says the object leaves 1m above the ground. how do i use the above formulas knowing this

 

[berkeman]

Homework Statement

A child throws a ball with an initial speed of 8.00 m/s at an angle of 40.0° above the horizontal. The ball leaves her hand 1.00 m above the ground and experience negligible air resistance.

(a) How far from where the child is standing does the ball hit the ground?
(b) How long is the ball in flight before it hits the ground?

Homework Equations

R(θ) = v₀^2(sin(2θ))/g for a
2v₀(sinθ)/g for b

The Attempt at a Solution

the above formulas assume that the object is at ground level, however the question says the object leaves 1m above the ground. how do i use the above formulas knowing this

Use the full set of kinematic equations for motion in a force field with constant acceleration (gravity). Are you familiar with them? Can you post them?

EDIT/ADD -- You don't need all of the equations (there are 3-4) for this problem, but it's good to be familiar with them anyway. You need different combinations of them for different problems...

 

[rashad764]

Use the full set of kinematic equations for motion in a force field with constant acceleration (gravity). Are you familiar with them? Can you post them?

EDIT/ADD -- You don't need all of the equations (there are 3-4) for this problem, but it's good to be familiar with them anyway. You need different combinations of them for different problems...

i'm not, can you post the ones that i need to know

 

[berkeman]

i'm not, can you post the ones that i need to know

I Googled Kinematic Equations for Constant Acceleration, and this is the first hit on the list:

http://www.physicsclassroom.com/class/1DKin/Lesson-6/Kinematic-Equations

This isn't covered in your textbook?

 

[rashad764]

I Googled Kinematic Equations for Constant Acceleration, and this is the first hit on the list:

http://www.physicsclassroom.com/class/1DKin/Lesson-6/Kinematic-Equations

This isn't covered in your textbook?

yes, i know those, but how do i use them with the angle?

 

[berkeman]

Write the equations for the vertical (y) and horizontal (x) positions as a function of time. The horizontal position only depends on the initial horizontal velocity (because there is no acceleration in the horizontal direction after the ball is released). The vertical position as a function of time depends on the initial vertical displacement, the initial vertical velocity, and the vertical acceleration (from gravity).

Please write out the equations that you think you should use, and work with them. The initial release point and velocities and the final impact point are related.

 

[rashad764]

x=v0t+x0
y=1/2at^2+v0t+y0

 

[haruspex]

x=v0t+x0
y=1/2at^2+v0t+y0

Ok, but you should distinguish horizontal velocities from vertical ones, not use the same symbol for both.
That gives you six variables on the right hand sides of those equations. Which of these do you have values for?