Physics problem help please? Energy problem!?

Its quite simple

Chimpo has Kinetic energy when he reaches the tire, and chimpo and the tire have P)otential energy when they have risen to the height of 2metres

Energy cannot be destroyed only converted

So total KE of chimpo = total PE of chimpo and the tire

0.5 x 80 v^2 = (80 + 20) x 10 x 2

40 x v^2 = 2000

V^2 = 2000/40 = 50

v = sqrt 50 = 7.07 ms is Chimpo's velocity

Using conservation of energy, you get that Ek=Ep (Kinetic energy= potential energy)

1/2mv^2 = mgh

1/2 x 80 x v^2 = (80+20) x (-9.8) x 2

v^2 = 100 x (-9.8) x 2 x 2/80

v^2 = 49

v = √49 = 7 m/s

That's your answer!

By the way the value of g is 9.8 not 10!

To all the students out there with teachers to impress, Physics is easy to do, just follow these steps: 1: You get a poisonous box 2: You put a cat in that box 3: You let it stay in the box And that's the way you do it!

Let

Po = initial momentum of Chimpo

P = final momentum of (Chimpo + tire)

Then

(1) ..... Po = Mc*Vo

where Mc = mass of Chimpo, Vo = initial speed of Chimpo

(2) ..... P = ( Mc + Mt ) * Vct

where Mt = mass of tire, Vct = initial speed of Chimpo and tire

By conservation of linear momentum (Po = P)

(3) ..... Mc*Vo = ( Mc + Mt ) * Vct

Now

(4) ..... Eo = (0.5)*( Mc + Mt ) * Vct^2 = initial energy of Chimpo

and tire at bottom of swing

(5) ..... E = ( Mc + Mt )*g*H = final energy of Chimpo and tire at top of swing

where H = 2.0 m

By conservation of energy (Eo = E)

.......... (0.5)*( Mc + Mt ) * Vct^2 = ( Mc + Mt )*g*H

(6) ..... Vct^2 = 2*g*H

From (3)

(7) ..... Vct = Mc*Vo / ( Mc + Mt )

Substituting (7) in (6)

.......... ( Mc^2)*(Vo^2) / [ ( Mc + Mt )^2 ] = 2*g*H

.......... Vo^2 = 2 * g * H * [ ( Mc + Mt )^2 ] / ( Mc^2)

(8) ..... Vo = SQRT { 2 * g * H * [ ( Mc + Mt )^2 ] / ( Mc^2) }

Substituting the values

.......... 2 * g * H = 2 * (9.8) * (2.0) = 39.2

.......... [ ( Mc + Mt )^2 ] / ( Mc^2) = [ ( 80 + 20 )^2 ] / [ ( 80 )^2) ] = 1.5625

.......... Vo = SQRT { ( 39.2 ) * ( 1.5625 ) } = 7.826

.......... 7.8 m/s = speed of Chimpo when he grabbed the tire