# Homework Help: Potato Launcher with Constant Velocity

1. Sep 27, 2011

### apierron

1. The problem statement, all variables and given/known data

As a participant in a robotic competition, you must launch a potato from a moving cart and strike a target. The potato must reach the apex of flight just as it travels over a screen, then it must pass through the center of an opening in a wall. The cart moves at a steady speed of 20cm/s (+x). The potato is launched from a height of 10 cm above the floor. The screen is 85 cm tall. The center of the opening in the wall is 20cm from the floor. The wall is 125cm to the right of the screen. The situation is diagrammed below (I attached a picture) How far from the screen should the potato be launched in order to make the shot?

2. Relevant equations

3. The attempt at a solution

So I used the information from the right side to find time from apex to the opening of the window and that help me find the velocity in the x direction and the angle but I don't know how any of this relates to the cart and now I'm stuck!!

#### Attached Files:

• ###### Physics.bmp
File size:
280 KB
Views:
160
Last edited: Sep 27, 2011
2. Sep 27, 2011

### Staff: Mentor

Last edited by a moderator: Apr 26, 2017
3. Sep 27, 2011

### Staff: Mentor

Since you have calculated an initial velocity and angle of launch for a potato launched from the center of the wall opening, you should be able to calculate how far away it would be from that launch point when it reaches the 10cm height on the other side of the screen.

4. Sep 27, 2011

### apierron

So kind of like going backwards?

5. Sep 27, 2011

### Staff: Mentor

Yes, just like going backwards! Projectile trajectories are reversible in this sense; if you have the "landing" parameters including speed and angle, you can fire a shot back along the original trajectory using that speed and angle to launch a projectile from that landing point.

6. Sep 27, 2011

### apierron

Ok thanks! I think I have it figured out. I was wondering what did the velocity of the cart have to do with anything?

7. Sep 27, 2011

### Staff: Mentor

Apparently, nothing at all. But I bet it distracted you