lecture chapter 5 part1

# Lecture chapter 5 - Newtons laws r(How to find a from given forces Newton#1 If the net force on an object is r r zero v is constant(stay rest or

This preview shows pages 1–4. Sign up to view the full content.

Newton’s laws: (How to find , from given forces?) Newton #1. If the net force on an object is zero, is constant. (stay rest or keep ) INERTIA (safety belt) Objects want to keep doing what they are already doing For example: in space …. (Attention: If friction, Air resistance… net force 0) Normal force N and gravity mg 2 forces on 1 object N and mg are 2 balanced forces. a r v r v r Newton #2 If net force 0 . is not constant, a 0 object’s acceleration will be in the same directions as the net force. v r a m F net r r =

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
SI Unit for forces : Newton (N) F= m a 1 Newton force (net force), will give 1 kg object 1 m/s 2 acceleration. 1 N = 1 kg. 1 m/s 2 1 N = 1 kg.m/s 2 Example : gravity, ( free fall, jump, projectile, same acceleration g. downward) G= mg weight = mass . g g= 9.81 m/s 2 Also g = 9.81 N/kg = 9.81 N/kg =9.81 kg . m/s 2 kg 1 kg object’s weight on earth is 9.81 N 100gram (about 3 oz) object weights about 1 N. Attention: when you solve problem, if you first convert every value to standard SI unit. (m, s, m/s, m/s 2 , N, ….) you can plug the numbers and automatically get SI unit in your answer.
Strategy: Always convert to SI unit before using equations. Example: = = = minutes 1 . 0 / 24

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 08/25/2010 for the course PHYS 111 taught by Professor Jamesm.lockhart during the Spring '09 term at S.F. State.

### Page1 / 13

Lecture chapter 5 - Newtons laws r(How to find a from given forces Newton#1 If the net force on an object is r r zero v is constant(stay rest or

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online