help help help?

Question

Member since: September 06, 2007
Total points: 20 (Level 1)
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miss_su_09
S Help please?
1.How much work can a 50.0 kg wrecking ball traveling at 5.00 m/s do on the building it strikes?
250
10
1,250
625

2A flower pot falls off a window ledge 10.0 m above the ground. Its velocity as it hits the ground is
unknown because we don't know the mass of the flowerpot.
20 m/s
14 m/s
10 m/s


3.A horizontal force of 275.0 N is exerted on a box with a weight of 745 N while moving it a distance of 2.0 m. How much work was done on the box? (calculate your answer in Newtons - just give me the number, no units in answer area) ?


4. A rock on the ground is considered to have zero potential energy. In the bottom of a well, then, the rock would be considered to have
no potential energy (all kinetic energy)
negative potential energy
zero potential energy, as before.
positive potential energy ?


5. If you do 600 J of work hoisting a 20 kg bale of hay, to what height did you lift it (in meters)?

Answer 1

1) The kinetic energy is available to do work
.5*50*25

=625 J

2) The time to the fall is found from
10=.5*10*t^2
t=sqrt(2)
the speed is
v=10*sqrt(2)
V=14

3)
745*2=1490 J

4) negative PE

5.600J=m*g*h
600/200=3 meters

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