# Recent content by solarwind

1. ### Question on significant digits

Hi all. Let's say I have a set of data as follows (the mass of a sample of some chemical measured several times): 23.132 g 24.532 g 21.532 g 22.853 g 23.193 g (I just made that data up, but imagine that a analytical scale put out those numbers, exactly as shown, on its display.)...
2. ### Projectile Motion of launched ball

And where exactly did you modify it so it takes into account that gravity is pointing down? Edit, nevermind I see it. Thanks so much!
3. ### Projectile Motion of launched ball

No, but I know your equation is right, I simulated it.
4. ### Projectile Motion of launched ball

Thank you! It works now. Why is it not negative? And thanks again for all your help! It's clear now!
5. ### Projectile Motion of launched ball

According to your equation, I did this: Solve[0 == -(14 + 0.08 (-9.81)) + 10 u - 0.08 (-9.81) u^2, u] It spits out: {{u -> -13.9493}, {u -> 1.20716}} So far, I have 3 different sets of answers (6 answers in total) which all seem to work out. There should be only 2 solutions. Which one is right?
6. ### Projectile Motion of launched ball

Well sorrrrryyyyyy! Can you explain how you got from the top two equations to the quadratic equations? I tried it but I'm getting imaginary numbers.
7. ### Projectile Motion of launched ball

I put in: Solve[25^2 == (10/t)^2 + ((14 + 4.9 t^2)/(t))^2, t] It gave me: {{t -> -4.43739}, {t -> -0.791265}, {t -> 0.791265}, {t -> 4.43739}} These two are the right answers for t: {t -> 0.791265}, {t -> 4.43739} All I want to know is how to get to this point on paper.
8. ### Projectile Motion of launched ball

Ok now I have all the equations I need: V[x]^2 + V[y]^2 = 25^2 = 625 14 = V[y] \Delta t - 4.9 t^2 10 = V[x] \Delta t I know how to do simultaneous equations. I have to solve for V[x] and V[y] from the second and third equations and plug that into the first one to get time. Then I can...
9. ### Projectile Motion of launched ball

[/B] That's exactly what I did but I don't know where to go from there.
10. ### Kinematics Equations (2 Problems!)

Haha! I know how that is... The answer is NO. This is because x could have a positive displacement and could also have a negative acceleration (slowing down) at the same time. Example, you roll a ball on the floor. It moves away from you (positive displacement) but is also slowing down...
11. ### Kinematics Equations (2 Problems!)

For your first question, what is x? Is it displacement, velocity or what?
12. ### Kinematics Equations (2 Problems!)

No, depends on reference. You can say gravity has a negative acceleration in the y prime, but a falling object is accelerating. The correct term is negative acceleration, not decelerating. Note: I could be wrong.
13. ### Projectile Motion of launched ball

Projectile Motion - Finding The Angle Homework Statement You are standing 10 m away from a basketball net that is 14 m above the ground. Assume delta d[y] is 14 m, do not account for your height. You launch the ball with a velocity of 25 m/s and it goes in the hoop. At what angle(s)...
14. ### Kinetic, potential and mechanical energy question.

Ok, I did this: a) Eg = mgh Ek = mv^2, where v I put 260 m/s Et1 = Eg + Ek b) Same thing as above but with the second values. Elost = Et1 - Et2. The answer is supposed tob e 5.5 x 10^9 Joules but i get 4.98 x 10^9 Joules. What did I do wrong? Did I go about this the right way?

Thanks dude!