# Newton’s Laws of Motion

Example: from Newton’s 1st law we know that an object travels in a straight line unless acted upon by an external force. A circular orbit is clearly not a straight line, what is the force? Newton showed that the planets are acted on by the force of gravity arising from the Sun. Each orbit is a constantly changing velocity where gravity adds a small “delta-vee” at each moment. This “delta-vee” is what produces the elliptical curvature that is the orbit.

Example: from Newton’s 2nd law when a baseball player throws a ball he applies a force, F, to the ball of mass m. Let’s say he throws a tennis ball of mass of one-tenth the mass of a regular baseball (1/10m). What is the resulting acceleration? Ten times the acceleration of a regular baseball and, therefore, ten times the final velocity and ten times the distance hit.

Example: from Newton’s 3rd law when a rocket is launched accelerating gases from the rocket engine push outwards from the rear. This inturn propels the rocket forward. This same principle can be seen when letting the air out of a party balloon.

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