Mass vs. Weight

1. Mass vs. Weight • Mass – The quantity of matter in an object. It is also a measure of the inertia or sluggishness that an object exhibits in response to any effort made to start it, stop it, or change its state of motion in any way (kg).

2. Mass vs. Weight • Weight –The force upon an object due to gravity. (N) Newton is the force applied to move a one-kilogram mass at an acceleration of 1m/s/s. Mass and weight are directly proportional to each other.

3. Mass vs. Weight 663 N = 150 lbf • Pound is a unit of weight in the USCS. • 1 pound = 4.448 Newtons • 130 pounds = 578.24 Newtons • Due to confusion, there are now two different abbreviations for the pound: • pound-mass (lbm) • pound-force (lbf) 663 N = 150 lbf

4. Mass vs. Weight • Mass does not change with gravitational force. • Inertia also does not change with gravitation force. (ex. shaking an object in space is just as difficult as it would be to shake it on Earth) • 1 kg = 10 N 150 lbm or 66.3 kg

5. Newton’s Second Law of Motion • Newton’s Second Law of Motion states: “The acceleration of an object is directly proportional the net force acting on the object, is in the direction of the net force and is inversely proportional to the mass of the object.”

6. Newton’s Second Law of Motion • Acceleration: • is caused by force • depends on the net force • Acceleration is directly proportional to the net force: acceleration ~ net force 2x acceleration = 2x net force • Whatever happens to acceleration will happen in equal quantity to the net force and vice versa.

7. Newton’s Second Law of Motion • Acceleration is also inversely proportional to mass. • As mass increases, acceleration with a constant force will decrease. • As mass decreases, acceleration with a constant force will increase. Acceleration ~ 1 . mass

8. Newton’s Second Law of Motion Acceleration ~ 1 . mass Acceleration ~ net force Put it all together… Acceleration ~ net force mass

9. Newton’s Second Law of Motion Acceleration of an object is always in the direction of the net force! Acceleration ~ net force mass “The acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.”

10. Newton’s Second Law of Motion Acceleration ~ net force mass A ~ Fnet m • If the ‘Fnet’ increases, ‘a’ will increase by the same amount • If ‘m’ decreases, ‘Fnet’ will increase by the same amount