# Tips on solving 2D Kinematic problems

1. Oct 9, 2011

### Goopy17

Hi,
This isn't a homework question. I need help on how to go about solving 2D kinematics problems. My teacher is terrible and doesn't even teach. It seems like it should be pretty straight forward with solving these, but i'm just having a hard time. If someone could give me tips on how to go about solving, it would make my life so much easier.
Thanks!

2. Oct 9, 2011

### bp_psy

Write down the given quantities at the top of the page. Write down what you are asked to do, You should read the question at least twice to be sure of what is asked of you. Begin solving the problem using symbols to represent quantities. Do not plug in numbers until the end.

3. Oct 12, 2011

### Ken G

The most important thing to remember in 2D kinematics problems is that the two dimensions are entirely independent of each other. So that means you are never actually doing a 2D kinematics problem, you are always doing two 1D kinematics problems at the same time. Literally-- t is the same in the two problems, that's all that connects them.

4. Oct 13, 2011

### Redbelly98

Staff Emeritus
I agree with Ken G. Furthermore, for each direction (x or y), you need to know 3 of the 5 quantities (displacement, initial velocity, final velocity, acceleration, and time) in order to solve for the motion.

For projectile problems, there is a constant velocity in the x-direction. So there is really just one equation describing the x motion:
Δx = vx·t​
In the y-direction, there is a constant acceleration of g acting downward. The kinematic equations you learned earlier in the course all apply here.

To completely solve a projectile problem you generally need to know:
(1) Two of the three quantities in the Δx = vx·t equation, and
(2) Three of the 5 quantities involved in the y-direction: Δy, vy,initial, vy,final, ay, and t. And you already know ay.

Last edited: Oct 13, 2011