College Physics (2D Motion)

[Cyanide]

Question: A daredevil decides to jump a canyon. Its walls are equally high and 10 meters apart. He takes off by driving a motorcycle up a short ramp sloped at an angle of 15 degrees. What minimum speed must he have in order to clear the canyon?

 

I've been picking at this one for an hour. I'm sure it's simple..

I realize that The horizontal distance is 10 meters..and acceleration for the x-component is 0. And that the acceleration for the y-component is 9.8 m/s^2.

I'm not asking for the answer.. I just need help getting started. I appreciate the help.

[swansont]

What equations are you using?

[Cyanide]

The equations I was given are:

v = v(initial) + at

Distance = (vi)(t) + 1/2a(t^2)

v^2= v(initial)^2 + 2(a)(distance)

[Cyanide]

I know that the horizontal acceleration is 0, so that distance =velocity x time

But I don't know the velocity so I can't find time, or vice versa

[swansont]

What is the displacement in the y direction at the time t when the motorcycle lands?

[Cyanide]

Since he technically goes up and back down...would his displacement in the y direction be 0 meters?

[swansont]

Since he technically goes up and back down...would his displacement in the y direction be 0 meters?

 

Yes. So you can solve the y equation for y=0. You'll get two answers, since it's a quadratic, but the "t=0" answer is not the one that you want. You should now have two equations (one in x and one in y) that depend on t and v. Two equations with two unknowns should be solvable.

[Cyanide]

Thanks for the help.

[Cyanide]

Again swansont I appreciate the help

 

Funny enough, I finally reached a reasonable answer...and it didn't agree with the back of the book. ...I was stuck on it for another hour

 

I went straight to my professor for help, as I thought perhaps I was dense... No. The question had been modified, but the answer hadn't been. Darn them.

[Klaynos]

I hate it when that happens! Seems to happen quite alot too, I recally my GCSE text book was terrible for it....

[hotcommodity]

I suppose its not too uncommon. The first calculus based physics book I got had a wrong solution for about every 10 problems. I got it from my Physics department when they were giving away books, I guess you get what you pay for =/