Veins contain a network of valves to insure a one-way flow of blood but arteries do not. this is because veins must counteract the force of on blood flow.

Quantum mechanics applies to subatomic, atomic, nanometer-size, and micrometer-size systems. nanometer, micrometer, and kilometer-size systems. atomic, nanometer-size, and micrometer-size systems. subatomic, atomic, and nanometer-size systems.

If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?

The ability to make things happen is also called a. heat b. force c. matter d. energy