PHYS1001 Lecture Notes - Lecture 3: Radioactive Decay, Net Force, Euclidean Vector
Lecture 3- Newton's Laws
Newton
ā¢ Described 3 fundamental laws ļ®
ā¢ Converted calculus ļ®
Newtonās first law (law of inertia)
ā¢ An object moves at constant velocity unless it interacts with another object ļ®
ā¦ In a straight line, at constant speed unless it experiences a force ļ®
ā¦ Inertia is a measure of how much resists a change in its motion ļ®
ā¢ The internal mass of an object is a measure of how much āinertiaā it has- more heavy,
harder to move ļ®
ā¦ How much force is required for a given change to its state of motion ļ®
ā¦ Given the symbol m- measured in kg ļ®
ā¢ On a merry go round you have to work to hold on because your body is resisting inertia
(it wants to keep going straight), if you fall off you will be thrown the way the
marry go round is going ļ®
Newtonās Second Law
F=ma, F=p/t
F= force, m= mass, a= acceleration, p= momentum (mv),
ā¢ The change in the momentum of an object is directly proportional to the net force
applied to it over a given time ļ®
ā¢ Known as impulse ļ®
ā¢ P=Fāt ļ®
ā¦ Exactly only for a constant force or ļ®
ā¦ If it is very small ļ®
ā¦ F is the net force- the vector sum of all forces acting on the object or system ļ®
āŖ Written as F(net)= F1 + F2 ļ®
ā¢ F= āp/āt ļ®
ā¦ P is the momentum ļ®
ā¦ How we define force ļ®
ā¦ Unit of force is newton N ļ®
ā¦ Unit of momentum newton seconds Ns ļ®
Types of forces:
ā¢ Gravity ļ®
ā¢ Electrical/magnetic ļ®
ā¦ Air resistance ļ®
ā¢ Strong nuclear ļ®
ā¢ Weak nuclear ļ®
ā¦ Radioactive decay ļ®
Net forces cause a change in motion
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