Section 3-2 Newtons first law What can cause the motion of a body? Force Take the apple's freely falling motion as an example What will be the states of the body if there is no any interactions between it and its environment? (an isolated system) At rest or 1D uniform motion Newton's first law Every body continues in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on itSection 3-2 Newton’s first law ▪ Newton’s first law : Every body continues in its state of rest or uniform motion in a straight line, unless it is compelled to change that state by forces impressed on it. ▪ What can cause the motion of a body? Take the apple’s freely falling motion as an example Force ▪ What will be the states of the body if there is no any interactions between it and its environment? (an isolated system) At rest or 1D uniform motion