Question

A boy reaches out of a window and tosses a ball straight up with a speed of 10 m/s. The ball is 20 m above the ground as he releases it. Use conversation of energy to find
Part A The ball's maximum height above the ground. Part B The ball's speed as it passes the window on its way down. Part C The speed of impact on the ground.

Answer 1

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The total energy TE = mgh + 1/2 mU^2; where h = 20 m, g = 9.81 m/sec^2, and U = 10 mps. When the ball reaches max height H, all that TE will be potential energy PE = mgH = TE.

So there you are. TE = mgh + 1/2 mU^2 = mgH = TE from the conservation of energy. Solve for H.

1) H = (gh + 1/2 U^2)/g = h + U^2/2g = ? meters where everything on the RHS is given. You can do the math.

2) As the ball drops from H to h, it picks up KE as the potential energy mgH is converted when the potential energy is diminished to mgh, where h < H. So PE - pe = ke = mg(H - h) = 1/2 mv^2 so solve for v = sqrt(2g(H - h)) and, again, everything is given. You can do the math.

3) Same deal as 2) except now its V = sqrt(2gH) because all the PE = mgH = 1/2 mV^2 = KE when it is about to hit the ground. You can do the math.

Answer 2

Answer:

A.25.096m

B.10m/s

V=22.189m/s

Explanation:

Part A The ball's maximum height above the ground. Part B The ball's speed as it passes the window on its way down. Part C The speed of impact on the ground.

newton's equation of motion

V^2= u^2+2as

a=-g since it is going against gravity

S=h s= distance travelled

h=height

V=final velocity

U=initial velocity

V=o

u=10m/s

0=100+2(-9.81)h

h=100/19.62

h=5.096m

The maximum height above ground level=

Height from thr window to the maximum the ball reached before coming downward+ height from the window to the ground level

H=h+h1

H=5.096+20

25.096m

2.part b

The final velocity as it reach its maximum height upward becomes zero and then the final velocity upward= the initial velocity when coming down

V=U =0

v^2=u^2+2ah

V^2=0+2(9.81)(5.096)

V=9.99917596605

V=10m/s

3. Speed of its impact on the ground

v^2=u^2+2ah

V^2=0+2(9.81)(25.096)

V^2=492.38352

V=22.189m/s