PHYS 1051 Lecture 5: Ch. 5 Newton's Laws of Motion Notes
Ch. 5 Newton’s Law of Motion Notes
Newton’s Laws of Motion
1st Law: Law of Inertia
oInertia- property of matter, which causes it to resist changes to its motion
Mass units: g, kg
oAn object at rest will remain at rest and an object in motion will remain in
motion in a straight line at a constant speed unless acted upon by unbalanced
force
oAnything not going in a straight line must have an outside force
oForce is a vector
oIf no unbalanced force acts on an object (summation of forces=0), there are 2
possibilities:
The object is at rest
The object moves with a constant velocity
2nd Law: Law of Acceleration
oThe effect of an unbalanced force is to cause an object to accelerate in the
direction of the force. The magnitude of the acceleration is directly proportional
to the magnitude of the force and is inversely proportional to the mass of the
object
oThe harder the push= the greater the acceleration
o1 kgm/s^2 = 1 Newton (SI unit of force)
oAs mass gets bigger, acceleration gets smaller
oForces cause acceleration
3rd Law: Law of Interaction
oWhen one object applies a force to a second object, the second object
simultaneously applies a force to the first object, which is equal in magnitude but
in the opposite direction
oForces always occur in equal and opposite pairs
oForces acting on different objects are unbalanced
oForces acting on same object are balanced
oAlways involves 2 forces and 2 objects; 1 force acts on each object
Relationship Between Mass and Weight
Object in freefall-gravity
Apply equal and opposite forces to put an object at rest
Mass x acceleration
Summary
1st Law- Inertia
oSum of forces= 0
oAt rest
oConstant velocity
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