物理
力、能量与运动
你要讲的内容 · 先选年级
3 年级共 6 个知识点
The Force of FrictionRubbing between surfaces slows things down, so a ball rolls farther on smooth ice than on rough grass.开讲 →The Pull of GravityAn invisible pull from the Earth makes every dropped thing fall down instead of up.开讲 →Balanced and Unbalanced ForcesWhen two pushes cancel out nothing moves, but when one side wins — like in tug-of-war — things start to move.开讲 →The LeverA stiff bar resting on a pivot point lets a small push lift something heavy, like a seesaw lifting a big kid.开讲 →The Inclined PlaneSliding something up a long slope takes less push than lifting it straight up — that's the trick of the ramp.开讲 →Wheels and PulleysWheels cut down friction and pulleys change the direction of a pull, so one rope can hoist a flag or a heavy load.开讲 →
往后的路 · 年级阶梯
Pick a grade · difficulty climbs 1 → 12
物理 across the grades
Grade 6Middle school
Speed & motion · forces and Newton's ideas