L4: FREE FALLING BODIES

False

T OR F: When dropped at the same height heavier objects fall faster than light objects because of their mass.

True

T OR F: Light objects fall with greater surface area tend to fall slower because of air resistance (air friction).

True

T OR F: In absence of air resistance, all objects will fall at the same rate regardless of the object's mass.

Galileo Galilei

• Was the first person to ask questions about the effects of mass to the speed of falling objects.

• He theorized that mass does not affect how fast objects fall.

• More than 350 years later, it was proven to be corrected by an astronomer David Scott in moon.

Free Fall

• The gravitation pull of the earth on an object results in a falling motion which is accelerated motion.

• The acceleration of an object varies with the distance of the object from the earth's surface.

• The acceleration of an object does not vary with the mass of the object.

• Any fallen body will experience air resistance, slowing down its motion.

Free Fall Definition

Constant acceleration of a body falling under the influence of the earth's gravitational attraction.

Free Fall Assumptions

• Neglect air resistance

• All bodies at a particular location fall with the same downward acceleration regardless of size and shape.

• Distance of fall is smaller compared to the radius of the earth.

• Ignore effects due to earth's rotation.

Constant acceleration due to gravity:

g = -9.8 m/s²

3 Cases of Free Fall

1. Object dropped at a certain height

2. Object thrown downward

3. Object thrown upward

Object drop at a certain height

An object drop at a certain height has no initial velocity

Object thrown downward

An object thrown downward has a non-zero negative initial velocity.

Object thrown upward

• An object thrown upward has a non-zero positive initial velocity.

• An object thrown upward follows time and speed symmetry.

• At the maximum height, the velocity is zero.

• It's upward velocity is positive and decreasing, while the downward velocity is negative but increasing.