Physics Newtons Laws Newtons First Law The Law

• Slides: 15

Physics

Newton’s Laws Newton’s First Law: The Law of Inertia. A body at rest and a body in motion continues to move at constant velocity unless acted upon by an unbalanced external force.

Newton’s Laws Newton’s Second Law: The Law of Acceleration. A net or unbalanced force acting on an object equals the mass of the object times the acceleration of that object.

Newton’s Laws For Centripetal acceleration:

Newton’s Laws Sample Problem: Find the acceleration of a 3 slug object acted upon by a net force of 1. 5 lbs.

Newton’s Laws Sample Problem: A 50 -kg block rests at the top of the plane whose length is 2. 00 m and whose height is 0. 50 m. How long will it take for the block to slide to the bottom of the plane when released?

Newton’s Laws Solution: Draw the vector diagram first.

Newton’s Laws Next establish the relationship:

Newton’s Laws

Newton’s Laws

Newton’s Laws Newton’s Third Law: The Law of Interaction. No matter what the circumstance, when one object exerts a force, the second must exert an exactly equal and oppositely directed force on the first.

Newton’s Laws For propeller problems, it is given by the formula: where:

Newton’s Laws Sample Problem: Each second a propeller accelerates an air mass of 12. 2 slugs from rest to a velocity of 137 ft/sec. How much thrust is provided?

Newton’s Laws Solution:

Exercises 1. Find the net force on a 5 slug object which is accelerating at 3 ft/sec? 2. At an altitude of 10, 665 m and a cruising speed of 252 m/sec, the Pratt & Whitney JT 9 D-7 F in the Boeing 747 has a mass flow of 879 kg/sec and an exhaust velocity of 306 m/sec. Find the thrust. 3. A 60 lb block rests on a smooth plane inclined at an angle of 20˚ with the horizontal. The block is pulled up the plane with a force of 30 lb parallel to the plane. What is its acceleration?