Chapter+4+Newton's+Laws

__Chapter 4: The Laws of Motion __ By: Steve Murray Newton's First Law of Motion:

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Newton's Second Law of Motion:

Force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration.

Newton's Third Law of Motion:

For every action, there is an equal and opposite reaction.

//__ Vocabulary __//
 * Inertia ** - The tendency of an object to continue in its original state of motion.
 * Mass ** - A measure of an object's resistance to changes in its motion due to a force.
 * Gravitational Force ** - The mutual force of attraction between any two objects in the Universe.
 * Tension ** - The magnitude of the force exerted along a rope.

__// Formulas //__

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__// Example Problems //__ 1. An airboat has a mass 420 kg, including the passengers, and has an engine that produces a net horizontal force of 750 N (After accounting for forces of resistance). Find the airboat's acceleration. 2. Find the gravitational force exerted by the Sun on a 70.0 kg man located on Earth. The distance from the Sun to the Earth is about 1.50 x 10^11 m, and the Sun's mass is 1.99 x 10^30 kg.

**Solution:** F_sun=G (mM_s)/r^2 =(6.67x 10^(-11) Nm^2/kg^2)(70.0 kg)(1.99x10^30 kg)/(1.50x10^11 m)^2 =0.413 N

3. An astronaut on a space mission lands on a planet with three times the mass and twice the radius of Earth. What is her weight (w_x) on this planet as a multiple of her weight w_E? **Solution:** w_x=G (3M_E m)/(2R_E)^2 =3/4 w_E

4. A steel box is laying on the ground with a coefficient of kinetic friction of 0.55. It is pushed with a force of 100 N. What is it's kinetic force? **Solution:** f_k=μ_k F_n=0.55 x 100 N=55 N

5. A mass is resting on a flat surface which has a normal force of 98 N. It's coefficient of static friction is 0.35. What force would it take to move the object? **Solution:** f_s=μ_s F_n=0.35 x 98 N=34.3 N