Projectile Motion: Solving for Range at Various Launch Angles

[ama]

Homework Statement

A shot-putter throws the shot with an initial speed of 4.0 m/s from a height of 4.5 ft above the ground. Calculate the range of the shot for each of the following launch angles.
a. 20 degrees
b. 30 degrees
c. 40 degrees
Vo=4
yo=4.5

Homework Equations

y = yo + Vo*sinθ*t - 1/2*g*t^2.
x = Vo*cosθ*t.

The Attempt at a Solution

I tried solving for the time in the first equation. I was careful to put in the height 4.5 for yo since it specifies that in the problem. I then tried to plug the time value into the second value. Then I repeated it for the other angles. Here is an example of what i did.
y=(4.5)+4(sin20)(t)-(1/2)(9.81)(t^(2))
y=4.5+1.36808t-4.9t^(2)
t=1.1081
x=4(cos20)(1.1081)
x=4.16509
For 30
4.1011499
For 40
3.8483
Yet for some reason these answers are wrong. Why?

 

[Doc Al]

I was careful to put in the height 4.5 for yo since it specifies that in the problem.

Note that the initial height was given in feet.

 

[tiny-tim]

welcome to pf!

hi ama! welcome to pf!

(try using the X² icon just above the Reply box )

… from a height of 4.5 ft
…
y=(4.5)+4(sin20)(t)-(1/2)(9.81)(t^(2))

erm …

feet! ​

 

[ama]

lol. I am so really new to physics.

 

[rwisz]

Your calculations appear to be correct, but it is important to note that the units for the initial speed (Vo) and initial height (yo) must be consistent. In this case, the initial speed is given in meters per second (m/s), but the initial height is given in feet (ft). To ensure accurate calculations, both values should be converted to the same unit, such as meters. Additionally, it is important to check for any rounding errors in your calculations that may affect the final answer.