Galilean Laws

• First Law: To determine if an object is at rest or moving with a constant velocity, identify a reference point. If the position of the object relative to the reference point does not change, the object is at rest. If the position of the object changes relative to the reference point at a constant rate, the object is moving with constant velocity.

• Second Law: To calculate the acceleration of an object, divide the net force acting on the object by its mass. The direction of the acceleration will be the same as the direction of the net force.

• Third Law: To determine the force required to keep an object moving at constant velocity, identify the forces acting on the object and calculate the net force. The force required to keep the object moving will be equal in magnitude but opposite in direction to the net force.

Kepler Laws

• First Law: To determine if an object’s orbit is elliptical, identify two foci of the ellipse. If one of the foci is the Sun, then the object’s orbit is elliptical.

• Second Law: To visualize a line joining a planet to the Sun sweeping out equal areas in equal times, imagine the planet moving along its orbit and drawing a line to the Sun. The line will sweep out equal areas in equal intervals of time.

• Third Law: To calculate the relationship between a planet’s orbital period and its average distance from the Sun, square the planet’s orbital period and cube its average distance from the Sun. The square of the orbital period will be proportional to the cube of the average distance from the Sun.

Centripetal Forces

• Centripetal Force: To identify the centripetal force acting on an object moving in a circular path, identify the force that is directed towards the center of the circular path. This force is the centripetal force.

• Magnitude of Centripetal Force: To calculate the magnitude of the centripetal force acting on an object moving in a circular path, multiply the mass of the object by its velocity squared and divide the result by the radius of the circular path.

Gravitation

• Gravitational Force: To calculate the gravitational force between two objects, multiply the masses of the two objects and divide the result by the square of the distance between them. The direction of the gravitational force will be along a line connecting the centers of the two objects.

• Acceleration Due to Gravity: To calculate the acceleration due to gravity near the surface of a planet, divide the gravitational force exerted by the planet on an object by the mass of the object.