Projectile Motion Problem: Calculating Time of Flight and Distance Traveled"

[!!!!!!!]

Before you get all worked up, I am just going to let you know that this isn't homework. Here is my problem : A projectile is fired at a 20 degree angle with a velocity of 15 m/s. What is the total time of flight? What is the distance of its height? How far did it travel in the horizontal direction?

Ok, no to solve this i used Vf^2=Vi^2-2ad, (this is on the trip up) where Vf = 0, Vi = 15, and a= 9.8, to give me the vertical distance of 11.48m. To find the horizontal distance, i used 15cos20 as the intial velocity and plugged it into the same equation to get a hor. distance of 10.13m. Then, to find total time i used a= (Vf-Vi)/t, where on the trip up a=9.8, Vf =0, and Vi = 15 to get a time of 1.53 sec, on the way down i used a=9.8, Vf=15, and Vi = 0 in the same equation to get the same exact time, which combine gave me a total of 3.06s...so all of my answers are as follows:
Dv=11.48m, Dh=10.13m, Ttotal=3.06s
If anyone could confirm or correct my process id be greatly appreciated. Also I am new so if this is indeed the wrong board i would gladly be redirected Thanks in advance

 

[radou]

Your answers don't seem correct.

Use the 'standard' equations for projectile motion:

$$v_{x}(t) = v_{0}\cos(\alpha)$$
$$v_{y}(t) = v_{0}\sin(\alpha) - gt$$
$$x(t) = v_{0}\cos(\alpha)t$$
$$y(t) = v_{0}\sin(\alpha)t - \frac{1}{2}gt^2$$.

 

[!!!!!!!]

Wow, my teachers hasnt given us those equations so I am really not sure how to use them

Your answers don't seem correct.

Use the 'standard' equations for projectile motion:

$$v_{x}(t) = v_{0}\cos(\alpha)$$
$$v_{y}(t) = v_{0}\sin(\alpha) - gt$$
$$x(t) = v_{0}\cos(\alpha)t$$
$$y(t) = v_{0}\sin(\alpha)t - \frac{1}{2}gt^2$$.

 

[radou]

Wow, my teachers hasnt given us those equations so I am really not sure how to use them

How to use them? Simply read them.

(Hint: use the condition y(t) = 0 to get the time of the flight t. Then you can find all you need.)

 

[!!!!!!!]

Wow! Excuse my terrible english in the previous statement..."my teachers hasnt...", you must think I am retarded

How to use them? Simply read them.

(Hint: use the condition y(t) = 0 to get the time of the flight t. Then you can find all you need.)

 

[radou]

Wow! Excuse my terrible english in the previous statement..."my teachers hasnt...", you must think I am retarded

Don't worry, this is no grammar forum.