can anyone help mw w/ this physics!?

Question

a .2 kg ball was released from a height of 12 meters. the ball hit the ground and rebounded to a height of 9 meters. (a) what was the vertical velocity of the ball just before it hit the ground? (b) what was the vertical velocity of the ball when it hit the ground? (c) the collision with the ground was inelastic because kinetic energy was lost. how much energy was lost to heat and sound in the collision with the ground?

Answer 1

In this solution I will ignore air friction.

a) using conservation of energy
.5*m*v^2=m*g*d
v=sqrt(2*g*d)
d=12
g=9.81

v=15.3 m/s

b) since the collision was inelastic, the vertical velocity was zero during the collision (unless you assume it moved the Earth a smidgen). I assume that the energy was converted into potential energy in the compression of the ball and heat and sound.

c) the energy lost to the collision (again ignoring air friction) was
E=m*g*(12-9)
E=.2*9.81*3
=5.89 J

j

Answer 2

enable n be the kind of hair dryers. Then the completed watt will grow to be 1500 n W. the optimal skill that's presented via the supply is P =VI = one hundred twenty*30 = 3600 W. So via equating 1500 n = 3600, we are able to get the cost of n as 2.4. So n shouldn't exceed 2.4. this skill somewhat 2 hair dryers would desire to be utilized. So in one 2d electric powered skill ate up could be 1500 J. For 8.a million hour there will be 8.a million*3600 seconds. So on a each and on a daily basis foundation the aptitude ate up could be 1500*8.a million*3600 J. In kilo watt hour, it is going to likely be arrived via dividing this via 3.6*10^6 J. it is composed of 12.15 kW hr. So the greater fee will come to $0.9477