I suck at physics

[Bambi005]

I hate required courses in college. I dont understand projectile motion so please help.

here are my problems. please help out of the possible 17 i couldt answer these 2.



1) The best leaper in the animal kingdom is the puma, which can jump to a height of 12 ft when leaving the ground at an angle of 45 degrees. With what speed, in SI units, must it leave the ground to reach this height?

2) A brick is thrown upward from the top of a bilding at an angle of 35 degrees to the horizontal and with an initial speed of 15 m/s. If the brick is in flight for 3.0 s, how tall is the building?

 

[nycxandy]

Just use the equations you were given and plug it in.

 

[Bambi005]

i tired but i got to this part of the chapter and bam. mind went blank and being up for 24+ hours doesnt help much either

 

[nycxandy]

Then take a rest and do it tomorrow.

It's all trajectory, just find the correct equation in your text.

 

[edro]

This is about as easy as physics gets... and I forget even this.

 

[MaxFusion16]

omg, projectile motion is the easiest topic in physics.
just think of it as 2 seperate motion in the x and y direction.
break it down to the x and y components and find out how long it takes the y component to hit the ground, then use that time to find how far it went in the x direction.
just plug in the equations.

 

[Cogman]

1. think of I triangle, 12 is height. use that and the gravity equasion and its derivitives. 1/2*g*t^2+V*t+s

 

[GasX]

1. do your own effing homework
2. it's basic trigonometry and algebra

 

[Triumph]

yes, the key is breaking it up into horizontal and vertical. just remember that as long as you're on earth, the horizontal component will have no acceleration and the vertical component will have gravity as an acceleration. for your tiger problem, all you have to look at is the vertical component. it's basically the same as doing a problem "how fast do you have to throw a ball to get it to go 12 feet high."

 

[DrPizza]

Originally posted by: MaxFusion16
omg, projectile motion is the easiest topic in physics.
just think of it as 2 seperate motion in the x and y direction.
break it down to the x and y components and find out how long it takes the y component to hit the ground, then use that time to find how far it went in the x direction.
just plug in the equations.

far from the easiest topic in physics... it's actually one of the more difficult topics for students to get a good grasp of.

If you still need a lot of help later, pm me... I should have a lot of free time tonight (after around 8pm) provided my wife works tonight. I'll see if I can get it to all make sense for you.
Personally, I hate the advice: plug it into formulas... There's no understanding involved when you do that.

incidentally, for the second problem, my advice to someone new to physics would be first to calculate the vertical component (an easy step), calculate the time going up, (subtract to get the time going down), how far it goes up, how far it goes down, and subtract the 2. Yes, I know you can do it in fewer steps - I'd just like to see you explain those fewer steps so that someone having trouble understands what's going on.

p.s. For what it's worth... your nic reminded me that I forgot to pack lunch. (leftover dinner from last night - mmm.. venison sandwich)