How do you solve motion in two directions problems in physics?
- Saturday Nov 28,2009 02:03 AM
- By diddy
- In Others
Having a little trouble with solving problems that have to do with projectiles in 2 directions. What should I look for in a problem to make it easier to solve? And how do I know that an answer is right?
Also, how should I organize my x and y values? Thanks alot.
Directions, Little Trouble, Organize, Physics, Projectiles, Solving Problems
One Comment
Projectile problems: You use the angle with horizontal to resolve the initial speed into x and y velocity components. Like vx = s cos(theta) and vy = s sin(theta) where s is the speed and theta the angle with horizontal. Then, you work the two directions sort of independently. In the x direction horizontal to the ground the projectile travels at constant speed so your equation is just dx = vx * t
In the y direction the projectile starts traveling up but slows from gravity pulling it back. The equation is dy = vy * t - (g/2)*t^2. Usually we do it this way so that dy = 0 at ground level. One thing to be careful about is putting all your known quantities into a consistent set of units like m/s, m/s^2, m and s. Then you put the known quantities into the equations and solve for the unknown.
If you have trouble getting started, you might try writing down the four equations I give here on your work sheet and then begin identifying which quantities you know and which you don’t.
Another thing to look out for is that physics problems often use realistic numbers where the answers must be done on a calculator and do not come out even numbers like you get used to in algebra classes. Messy looking decimal numbers are ok as answers, but you need to be careful about checking your answers because you can’t just look at it ans see it is ok.
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