Posted by **Angela** on Sunday, October 14, 2012 at 12:59pm.

A ball of mass 522 g starts at rest and slides down a frictionless track, as shown below. It leaves the track horizontally, striking the ground a distance x = 0.81 m from the end of the track after falling a vertical distance h2 = 1.03 m from the end of the track. (a) At what height above the ground does the ball start to move?

(b) What is the speed of the ball when it leaves the track?

(c) What is the speed of the ball when it hits the ground?

- Physics -
**Elena**, Sunday, October 14, 2012 at 4:24pm
m•g•h1=m•v²/2

v=sqrt(2•g•h1)=v(x)

t=x/v =x/v(x) =x/ sqrt(2•g•h1)

h2=g•t²/2=g• x²/ 2•2•g•h1=x/4•h1 =>

h1=x/4•h2=0.81/1.03 =0.79 m

(a) H=h1+h2= 1.03+0.79=1.82 m.

(b) v=v(x)=sqrt(2•g•h1)=

=sqrt(2•9.8•0.79) = 3.93 m/s.

(c)

t=x/v(x)=0.81/3.93 = 0.2 s.

v(y) = gt=9.8•0.2= 1.96 m/s.

v=sqrt{v(x)²+v(y)²} = sqrt(3.93²+1.96²) = 4.4 m/s.

- Physics -
**Angela**, Sunday, October 14, 2012 at 6:05pm
Those were all wrong, I don't get it.

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