What is the final velocity of the ball?

[rzlblrt417]

Homework Statement

a ball hits a wall at 60 degrees from the wall and leaves the wall at 60 degrees.

v1 = 10 m/s
v2 = 10 m/s
m = 3.00 kg
t = 0.200s

Homework Equations

p = mvcos(angle)
J = p2 - p1

The Attempt at a Solution

p = (3.00)(10)(cos(60))
p1 = 15
p2 = 15

and that is as far as i can get. I am not sure how time plays into this. Any help is appreciated. I have the text in a few hours. Thank you

 

[grzz]

what is being asked for?

 

[sankalpmittal]

Homework Statement

a ball hits a wall at 60 degrees from the wall and leaves the wall at 60 degrees.

v1 = 10 m/s
v2 = 10 m/s
m = 3.00 kg
t = 0.200s

Homework Equations

p = mvcos(angle)
J = p2 - p1

The Attempt at a Solution

p = (3.00)(10)(cos(60))
p1 = 15
p2 = 15

and that is as far as i can get. I am not sure how time plays into this. Any help is appreciated. I have the text in a few hours. Thank you

As grzz said , I cannot understand what you are trying to find out. Anyways what's the question asking for ?

 

[rzlblrt417]

My apologies, I always do that. Force on by the wall on ball

 

[rzlblrt417]

*by wall on the ball

 

[sankalpmittal]

*by wall on the ball

Got that ! Ok so what is p₁ ? Or I mean momentum of the ball before striking the wall ?

Then you find out p₂ or the momentum of ball after it stroke the wall.

What do you get ?

 

[rzlblrt417]

Got that ! Ok so what is p₁ ? Or I mean momentum of the ball before striking the wall ?

Then you find out p₂ or the momentum of ball after it stroke the wall.

What do you get ?

the same thing for p1 as p2?

 

[rzlblrt417]

14.7n?

 

[sankalpmittal]

the same thing for p1 as p2?

No p1 and p2 aren't same. Be careful regarding geometry.

Hint : see the image : http://postimage.org/image/qvnhzhnsl/

Above answer is wrong.
Look at image

 

[rzlblrt417]

No p1 and p2 aren't same. Be careful regarding geometry.

Hint : see the image : http://postimage.org/image/qvnhzhnsl/

ok so then

p1 = (3.00)(10)cos(30)
p2 = (3.00)(10)cos(60)

so p2 - p1 = -14.133 so then it would just be 14.133N?

or is it sin(30) making it 14.5N

 

[sankalpmittal]

ok so then

p1 = (3.00)(10)cos(30)

Correct.

p2 = (3.00)(10)cos(60)

Right !

so p2 - p1 = -14.133 so then it would just be 14.133N?

or is it sin(30) making it 14.5N

Nope. What about time t ?
From Newton's second law : F= Δp/Δt = p₁-p₂/t

Plug in it. What do you get ?
Do calculations properly. You got it wrong for p1-p2 also.

 

[rzlblrt417]

Correct.



Right !



Nope. What about time t ?
From Newton's second law : F= Δp/Δt = p₁-p₂/t

Plug in it. What do you get ?
Do calculations properly. You got it wrong for p1-p2 also.

OH! ok so then after plugging everything in i got 71.6N!

 

[sankalpmittal]

OH! ok so then after plugging everything in i got 71.6N!

Your method of evaluation is correct but calculations are wrong. Do you know the value of cos 60^o and cos 30^o ? What are they ?