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A ball of mass 2 kg is gently pushed off the edge of a tabletop that is 1.8 m above the floor. Find the speed of the ball as it strikes the floor. |
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Answer» Solution :IGNORING the friction due to the air, we can apply coservation of mechanical energy. Calling the floor our h=0 reference level, we write `K_(i)+U_(i)=K_(f)+U_(f)` `0+mgh=(1)/(2)mv^(2)+0` `v=sqrt(2gh)` `=sqrt(2(10m//s^(2))(1.8m))` `=6m//s` Notice that the ball's potential energy decreased, while its kinetic energy increased. this is the BASIC idea behind conservation of mechanical energy: One form of energy decreases while the other increases. (ALSO, notice that although the question gives you the MASS of the ball, it wasn't necessary since the mas m cancelled out of the equation.). |
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