This chapter explored how forces influence motion over time, using Newton’s laws as a powerful but limited model. At atomic scales, Newtonian mechanics gives way to quantum mechanics, where particles ...This chapter explored how forces influence motion over time, using Newton’s laws as a powerful but limited model. At atomic scales, Newtonian mechanics gives way to quantum mechanics, where particles behave as probability waves. At high speeds, special relativity modifies our concepts of space and time. Newton’s laws remain useful for most everyday phenomena, though quantum and relativistic effects reveal the boundaries of classical physics.