# Lecture 1: Forces and Newton's laws

When emailing the lecture-note to imechanica@gmail.com with the subject title as Lecture 1, please also put your information in the text message: Name, University ID, and Aerospace/Mechanical Engineering. Thanks.

1. A force is a relationship
2. A force is a vector

3rd law

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

2nd law

Force is a vector, F
Acceleration is a vector, a
F=ma

Galileo’s experiment
Leaning tower of Pisa
No matter what the difference in weight, two heavy objects will fall simultaneously at virtually the same speed
Experiment: drop of two objects with different masses
Resistance from air

a=F/m
Massive the object, more tends to resist changes in its state of motion
helmet  (design issue, protection and mobility)

1st law

An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

back to MACE-11010  Engineering Mechanics
back to MACE-11010 Calendar

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### still Missing

Dear Mr. Tan,

Yesterday (thursday, 4th oct.) there werent enough pages of notes to go around...and I asked you for some extras. You said they would be here, and so far they are not. When should I expect them here?

Thank you,

Rafael