Force, mass, and acceleration

When forces are unbalanced on an object it causes a change in motion such that the object accelerates.

Acceleration: Change in velocity.

The stronger the force, the stronger the acceleration.

The larger the mass, the larger the force has to be.

Think about the two sentences above. What force does it take to move a paper clip? An automobile?

If the forces are balanced on an object then the motion does not change, its either at rest or constant velocity. (Newton’s First Law)

When the forces on an object do NOT add up to zero then they are unbalanced. They will produce acceleration. Such as

Pull force

friction

Force has both magnitude (how much) and direction.

North or South or East or West or

1200 N – 800 N = 400 N

600 N – 800 N = - 200 N

In the third example the upward and downward forces balance so the only force left is the 20 N force to the left.

Up is +YDown is –YRight is +XLeft is -X

The formula:

Force = mass x acceleration

F = m x a

Example: If the mass is 50 Kg and the acceleration is 2 m/s2 then

F = 50 x 2 or 100 N

Example:

Reminder: F = m x a

Units for Force: Newton Units for mass: kg Units for acceleration: m/s2

If a force of 16 N acts on an 8 kg mass then what is the acceleration?

F/m = a 16/8 = 2 m/s2

1. Force is a vector: Direction matters as well as magnitude (how much).

Up is + Y down is - Y Right is + X 500 N up + 700 N down = Left is - X 200 N down

400 N left + 950 N right = 550 N right

F = m x a Force = mass x acceleration If the force is 75 N to the right on an object and the object has a mass of 5 kg then F = 75 N m = 5 kg 75 N = 5 x a or 15 m/s2 to the right or its + 15 m/s2

y

x-x

-y