Physics problem, plz help!?

Question

Bert and Ernie are standing on a ladder picking apples in Mr. Hoopers orchard. As they pull each apple off the tree, they toss it into a basked that sits on the ground 3.0m below at a horizontal distance 2.0 m from them. How fast must Bert and Ernie throw the apples (horizontally) in order for them to land in the basket.

The Givens are...
delta y = -3.0 m
delta x = 2.0 m
gravity = 9.8 m/s^2

The Needs are...
initial velocity = ?

Please help, i cant find initial velocity but im sure the answer is right in front of my face. I looked at all my equations but i still cant seem to figure out how to solve for initial velocity.


delta x = (Vix)(t)
Vix= Vi cos(pheta
Vy(final velocity) = Viy -gt
delta y = viyt - 1/2gt^2
Vy^2 = Viy^2-2g(delta y)
Viy = Vi sin(pheta

Answer 1

The apples fall vertically 3.0 meters downward. If t is the time it takes to fall, the following must be true.



3 = (1/2)gt^2 = (0.5)(9.8)t^2

t^2 = (3.0)/(0.5)(9.8) = .61

t = .78 seconds



In this time, the apples must travel horizontally 2.0 meters to reach the basket. So they need to travel with an initial horizontal velocity of:



v = (2.0 meters)/(0.78 seconds) = 2.56 meters/seconds

Answer 2

First u will need to figure out how long it takes to fall into basket. Since you will be throwing in the horizontal direction only, gravity will be the only force downward, so Viy will be zero.



So using delta y = viyt-1/2gt^2 = 0 - 1/2gt^2 = -3. So t = 0.7824 secs.



And since the only force is horizontal Vix = Vi . So using delta x = (Vix)t find Vix



Vi = Vix = delta x / t = 2/0.7824 = 2.556 m/sec

Answer 3

Ok, well maybe we should just work backwards a little bit from here.



Finding the time the apple is in the air would be really useful for this problem. So we have the gravity constant, and we know how far the apple fell, so we can determine the time it was in the air with this equation:



d = -4.9t^2

-3.0 = -4.9t^2

here we substitute in the vertical distance



0.612 = t^2

divide by -4.9



0.782 = t

square root to find t



ok with the time we can easily solve this. assuming the apple was thrown horizontally at a constant velocity, and neglecting air resistance, we have everything we need.



d = rt

2.0 = r(.782)

simply plug in the distance and time into this formula



r = 2.56 m/s

Answer 4

You know you have to resolve this into vertical and horizontal components...

For the vertical, since the apple's thrown horizontally, there is NO vertical velocity. So, you can solve vertically for t...

d = 3

a = 9.8

vi = 0

t = ?



And then continue with the horizontal component:

d = vt

d = 2

t = what you got from above

v = ?



Hope that helps =)

Answer 5

I can answer one of your questions. 1) Water is not densest at 4* Celsius. Let me explain myself. When any other element / liquid is cooled, its density constantly decreases as the temperature is lowered. However this does not apply on water. When water is cooled till 4* Celsius, its shows decrease in density but when the temperature is brought anywhere between 4* Celsius - 0* Celsius, it's density slightly increases. This is known as anomalous expansion of water. So in countries which have temperature less than 0* Celsius, water freezes to form snow. Also the snow is less dense and does not dissolve in water. Instead it evaporates. Therefore snow fall is possible in countries having temperature less than 0* Celsius. I will try to look for an answer to your second question. -- Broledh

Answer 6

t= square root of (2y/9.8)



take 2*3m divided by 9.8m/s^2 to get time

and take 2m divided the time you got to get velocity