A ball is thrown toward a cliff of height h with a speed of 30m/s and an angle of 60 degrees above horizontal. It lands on the edge of the cliff 4.0s later. How high is the cliff? do you just use the equation h=.5gt^2 ? and put it in -9.80=g and 4=t ?
You also need to consider the initial speed in the y-direction; here's the complete equation: [tex]y = y_0 + v_{0y} t - (1/2) g t^2[/tex]
would this be correct: y0=26 , v0=30, g=-9.8 , t=4 ... so y=26+(30x4)- .5(-9.8)(4)^2 = 224.4 m ? i got vy by doing v0sintheta= 26
No. In the formula I gave: y0 is your initial position, which I presume is on the ground at height = 0 v0 (which I'll change to v0y) is the vertical component of the initial velocity, what you call v0sin(theta) g = 9.8 m/s^2 To make it less confusing, I'll relabel v0 to be v0y in my equation.
thanks! can you help me with the next part too..! What was the maximum height of the ball? i think the equation is just the same as the one you wrote, but just cut t=4 in half to get the peak height so t=2 ..so y= 26(2)-.5(9.8)(2)^2 = 32.4 m ?
No, you can't assume that the peak is at half the time. After all, it lands up on a cliff, so it spent more time rising than falling. (If it fell back down to the original height, then you'd be correct.) Instead, use a velocity equation for the y-direction to figure out the time when it reaches maximum height. Hint: At the maximum height, what's the vertical speed?
so would it be okay to use the equation vfy= viy +ayT so 0= 26+9.8t so t= 2.65 and then cut then stick that time in that first equation you gave me?
What is the ball's impact speed? i thought what you should do is find the final velocity in the x component and y component. and i thought that vfx= 15 since there is no acc in the x direction and vfy= -26 b/c of neg acc. and then i thought you should take the magnitude, but this does not work out to be right. do you know what i am doing wrong wait i think i did this wrong, look at my next post please
oh no actually should vfy= 65.2 because i tried the equation vfy=viy+ay x T so 26+(9.8x4)= 65.2 so do i do square root (15^2 + 65.2^2) = 66.9 ?