# Homework Help: Cue ball kinetic energy

1. May 4, 2010

### say_uri

a)A pool Cue exerted an average force of 160N on a cue ball over a distance of 0.012m How much work did the cue do on the ball.

b)If all the work done on (a) was transformed into kinetic energy of 0.0200kg cue ball, what was the speed of the ball?

c) Light from the sun reaches the earth in 8.3min. The speed of light is 3.00x10g m/s. in kilometer, how far is the earth from the sun?

d)An electron travels at a unifor velocity of 3.2x10g m/s, how much time is required for a displacement of 1.0m?

e)A person walks 5.0 km torwards the east in 2.0 hours,then 1.5 km towards the west in 0.5 hour, and finally 10.0 km torwards the east again in 2.25 hour. What is the person's average velocity?

2. May 4, 2010

### rock.freak667

Re: Physics

You need to show some attempt before anyone here can help you.

What is the definition of work done and kinetic energy?

How would you find distance given speed and time?

How do find time given distance and velocity?

What are the individual velocities for the journey?

3. May 5, 2010

### say_uri

Re: Physics

well for a and b , i tried it. but i dont think it is correct.

a) w=f^d
w=160Nx0.012m
w=1.96

b) Ek=1/2mv2
i canceled , then ended up with √ 2x0.0200/1.92
V= 0.14433756729741

and for the rest of the questions i need help with the equations to use for.
c,d,and e
thanks

4. May 5, 2010

### rock.freak667

Re: Physics

You should have gotten

$$v = \sqrt{\frac{2E_k}{m}}$$

Check it again.

For c an d, if you multiply speed and time, what do you get?

5. May 5, 2010

### say_uri

Re: Physics

for c,d and e.
C) i got 2490 km
8.3x30=2490

D)320 000 3.2x100 000

E)5.0x2.0=10
1.5x0.5=0.75
10.0x2.25=22.5

i dont know what to do next?

6. May 5, 2010

### say_uri

Re: Physics

for b,
i calculated again , is this one right?
0.01041666666667

7. May 5, 2010

### rock.freak667

Re: Physics

What are you using for the speed of light and the speed of the electron? I don't think you mean 'g' to be 9.81 m/s2

Ek is the work done in part a).