Muscles make it possible for animals to move. They are attached to the bones. Most muscles are controlled by the brain. Messages from the brain travel through nerves and tell the muscles when to act. Unused muscles go soft. Exercise and a proper diet that includes lean meat, milk, and cheese help to build strong muscles.
The force Of Friction
When two surfaces are rubbed against one another, one tends to stick to the other. Friction is the force that causes this. No surface is perfectly smooth. Even the smoothest looking surface, when examined with a microscope, will be seen to have bumps and hollows. These bumps and hollows resist one another when two surfaces are rubbed together. The force of resistance is called friction. Friction can be useful. Rub the palms of your hands together, pressing hard. Do this quickly several times. Your hands begin to feel warm. This shows that friction produces heat.
No comments:
Post a Comment