Finding Acceleration without Time: Help Clarified

[majormuss]

Homework Statement

Guys, this question is really frustrating me. Ho can I can I Find time when magnitude of acceleration when time is not giving, and also the object is not moving vertically(so I can't use a=9.81m/s?... I tried using (Change in velocity)V= Acceleration* Time,but I eventually get stuck!
Can anyone help Clarify things to me.

Homework Equations

(Change in velocity)V= Acceleration* Time

The Attempt at a Solution

 

[tiny-tim]

Welcome to PF!

Hi majormuss! Welcome to PF!

(what exactly is the question? )

If the projectile starts at an angle to the vertical, then you need two equations, one for the vertical component of motion with a = -9.81 m/s², and one for the horizontal component with a = 0.

 

[majormuss]

Hi majormuss! Welcome to PF!

(what exactly is the question? )

If the projectile starts at an angle to the vertical, then you need two equations, one for the vertical component of motion with a = -9.81 m/s², and one for the horizontal component with a = 0.

thnx for the response, but when I assume Acceleration is 0 for horizontal motion my equation ends up... V(f)-V(i)/a... then i get a denominator of 0, which makes it undefined. I can't find time

 

[pgardn]

thnx for the response, but when I assume Acceleration is 0 for horizontal motion my equation ends up... V(f)-V(i)/a... then i get a denominator of 0, which makes it undefined. I can't find time

Well Vf and Vo should be the same for the horizontal because it does not change while in the air (assume no air friction). The previous poster stated there is no acceleration in the horizontal.

In many of these projectile problems, time is usually determined by info. given about motion in the vertical in which case you use your -9.81 m/s/s as your acceleration.

 

[tiny-tim]

thnx for the response, but when I assume Acceleration is 0 for horizontal motion my equation ends up... V(f)-V(i)/a... then i get a denominator of 0, which makes it undefined. I can't find time

As pgardn says, V_ix and V_fx are the same.

I see now that the problem is that you're only using one of the constant acceleration equations …

(Change in velocity)V= Acceleration* Time

There are two others!