[填空题]
1.Define potential energy.
2.A body of mass $2.0\,kg$ is pushed with an initial speed of $1.2\,m\;s^{-1}$ down the slope of a frictionless $30^{\circ}$ incline from a height of $h$. As soon as it reaches the bottom of the incline, it begins to move on a rough horizontal table where it comes to rest momentarily after colliding with a spring of spring constant $32\,N\;m^{-1}$.
1.The speed of the body is $3.06\;m\;s^{-1}$ when it reaches the bottom of the incline. Calculate $h$ $m$.
2.The distance between the bottom of the slope and the body's position is $x$. On the graph, sketch the variation of the square of the speed $v^2$ of the body with distance $x$.(no need to add values to the axes)
3.At the instant that the body stops momentarily, the spring is compressed as $0.43\,m$. The coefficient of friction between the body and the rough surface is 0.40. The distance that the body covered on the horizontal rough surface between the point of leaving the ramp and stopping momentarily.
3.The incline is replaced with one of a steeper gradient. The body is pushed at the same speed from the same height. Explain the effect of the increase in gradient on the maximum compression of the spring in comparison to the maximum compression in the original situation.
