help.. physic help!! plz help?

Question

1.a physics student lifts her 2kg pet rock 2.8m straight up. He then lets it drop to the ground. Use the Law of Conservation of Mechanical Energy to calculate how fast the rock will be moving (a)half way down and (b)just before it hits the ground
2.A 65kg girl is running with a speed of 2.5m/s. How much kinetic energy does she have? She grabs on to a rope which is hanging from the ceiling, and swings from the end of the rope. How high off the ground will she swing?
3.How much kinetic energy will the 80kg skier sliding down the frictionless slope have when he is 2/3 of the way down the ramp? The vertical height of the ramp is 60m.
4.A rubber ball falls from a height of 2m, bounces off the floor and goes back up to a height of 1.6m. What percentage of its initial gravitational potential energy has been lost? Where does this energy go? Has the Law of Conservation been violated?
5.How much work must be done to increase the speed of a 12kg bike ridden by a 60kg from 8.2m/s to 12.7m/s?

Answer 1

Conservation of energy states that
KE=.5*m*v^2
and
PE=m*g*h
so
v=sqrt(2*g*h)

At 1.4 m
v=sqrt(2*g*1.4)

at the ground
v=sqrt(2*g*2.8)

2. .5*65*2.5^2 is the KE
the height is related as in 1
.5*2.5^2=g*h
or h=.2*2.5^2/8

3. m*g*h=
80*g*60*2/3

4. 1.6/2
The energy goes into heat as a non-conservative bounce occurred.

5 Energy and work are related
so
work=.5*m*(v2^2-v1^2)
or
.5*12*(12.7^2-8.2^2)

j

Answer 2

Waves are frequently defined with the aid of variations in some parameter with the aid of area and time—to illustrate, top in a water wave, stress in a valid wave, or the electromagnetic container in a easy wave. the fee of this parameter is noted as the amplitude of the wave, and the wave itself is a function specifying the amplitude at each ingredient. In any equipment with waves, the waveform at a given time is a function of the components (i.e., exterior forces, if any, that create or impression the wave) and preliminary circumstances of the equipment. in lots of circumstances (to illustrate, in the classic wave equation), the equation describing the wave is linear. while it is genuine, the superposition thought would properly be utilized. meaning that the internet amplitude brought about with the aid of 2 or extra waves traversing an identical area, is the sum of the amplitudes which could have been produced with the aid of the guy waves one after the other. to illustrate, 2 waves traveling in the direction of one yet another will pass good with the aid of one yet another with none distortion on the different area.