ch4 - Ch 4 Newton's 2nd Law force mass and acceleration...

1
Ch. 4 - Newton’s 2nd
Law
force, mass, and acceleration,
What causes acceleration?

A “push” or “pull” applied to an object causes the object to move.

The “push” or “pull” is a FORCE.

The change in velocity (rest to moving) is an ACCELERATION.
Force is proportional to Acceleration
F ~ a
Force and acceleration
a ~ F
2a ~ 2F
3a ~ 3F
What relates the two terms?
MASS
m

2
Newton’s Second Law
The acceleration of an object is directly proportional
to the net force applied and inversely proportional to
the mass.
∑ F = F
net
= ma
a = F
net
/m
Mass, m - kilograms (kg)
Acceleration, a - m/s 2
Force, F - kg-m/s 2
1 kg-m/s
2
= 1 N (Newton)
Forces in Nature
Forces : cause a “push” or “pull” on an object.
There are FOUR fundamental forces in nature:
• Electromagnetic (force between charged particles)
• nuclear strong (force between nuclear components)
• nuclear weak (another force between nuclear components)
• gravitational (very weak force between all matter)
Most of the “forces” we encounter in our common experience
are EITHER gravitational or electromagnetic in nature (e.g .,
weight, friction, drag, traction, tension, etc.).
“New” forces?
• Modern physics theories suggest that when the universe was
very young (<< 1 second), these four forces were combined
into a single force.
• One goal of physics research is to find a single theory that