平衡力与不平衡力

规划并开展一项探究活动，用证据说明平衡力和非平衡力对物体运动的影响。

Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object

学习证据 / Evidence

• 定义平衡力（大小相等、方向相反——物体运动状态不变）和非平衡力（导致物体运动状态改变）。
• 设计一个公平实验，探究不同大小的力如何影响物体的运动。
• 利用实验结果作为证据，解释什么时候力是平衡的，什么时候是不平衡的。

• Define balanced forces (equal in size, opposite in direction — no change in motion) and unbalanced forces (cause motion to change)
• Plan a fair test investigating how different force sizes affect an object's motion
• Use results as evidence to explain when forces are balanced versus unbalanced

评估问题 / Assessment

{{name}}能解释为什么放在桌子上的书不动（平衡力），而当你推它时却会滑动（非平衡力）吗？

Can {{name}} explain why a book sitting on a table doesn't move (balanced forces) but slides when you push it (unbalanced forces)?