Physics question - Easy for you, hard for me!

[Bram Turismo]

Right now, we're learning about Work and energi with vectors.

In this exercise, I've got to find the following things:

a) How much work (J) does the thrower exercise on the ball?
b) How much speed has the ball when it comes down?

This is the exercise:
A ball is attached to a rope, and a throwing person is about to shoot it in the air. In the first stage, I know:

-speed of the ball (10m/s)
-height of the ball above ground: 1,10m
-mass of the ball: 7,25 kg

In the second stage, the speed rises to 22 m/s. I've got the following information:

-height of the ball above the ground is still 1,10m
-speed: 22m/s
-angle created between the line of the ball and the line where it's 1,10m above ground: 42 degrees


Now, the main rule we learned about W, work: W=F.s.cos(angle)

I just can't figure it out, I've tried to find potensial and kin. Energi (Ep and Ek), but I can't see the link between E and W here. I do not know time (t), nor distance (s). I can use gravity on the objects, but I can't spot a connection here either...


Suggestions?

 

[PeterJB]

Thats a really confusing question!

 

[Stevisiov]

Thats a really confusing question!

Well acctually its easy if you know how to do it, it just requires a logical approach. Unfortunetly I no longer have my projectiles notes that would allow me to help Bram with this one.

 

[GT4 genius]

Right now, we're learning about Work and energi with vectors.

In this exercise, I've got to find the following things:

a) How much work (J) does the thrower exercise on the ball?
b) How much speed has the ball when it comes down?

This is the exercise:
A ball is attached to a rope, and a throwing person is about to shoot it in the air. In the first stage, I know:

-speed of the ball (10m/s)
-height of the ball above ground: 1,10m
-mass of the ball: 7,25 kg

In the second stage, the speed rises to 22 m/s. I've got the following information:

-height of the ball above the ground is still 1,10m
-speed: 22m/s
-angle created between the line of the ball and the line where it's 1,10m above ground: 42 degrees


Now, the main rule we learned about W, work: W=F.s.cos(angle)

I just can't figure it out, I've tried to find potensial and kin. Energi (Ep and Ek), but I can't see the link between E and W here. I do not know time (t), nor distance (s). I can use gravity on the objects, but I can't spot a connection here either...


Suggestions?

If you could explain it a bit better I would love to be ale to help, starting a physics degree in a month, I would want to know how to do these! And if your 'main rule' is derived from vectors then thats the modules of F multiplied by the modules of s multiplied by cosine of the angle. I think, been a long summer, things become hazy.

 

[Tornado]

Does A go with the first stage and B go with the second stage?

 

[Bram Turismo]

Does A go with the first stage and B go with the second stage?

No, both go with B... I can't figure out if I could use the speed in the first stage as a startspeed in the second phase? (eg. to use v^2 - v0^2= 2.a.s, etc.)


EDIT

Solved, I had to use difference in Energi (Ek, I always confuse it with "Chinese" energi): 1/2.m.v^2-1/2.m.v0^2