The speed of a falling object is?not?proportional to its mass.

all objects?would?fall?with the same constant acceleration in the absence of air or other resistance.

at a given location on the Earth and in the absence of air resistance, all objects fall with the same constant acceleration.

g?=?9.80 m??/s^2?

Acceleration due to gravity is a vector, as is any acceleration, and its direction is down ward toward the center of the Earth.

where delta?v?is the change of velocity during the time interval?￠t.?Instantaneous acceleration?is the average acceleration taken over an infinitesimally short time interval.

If an object has position?x0?and velocity?v0?at time?t?=?0 and moves in a straight line with?constant acceleration, the velocity?v?and position?x?at a later time?t?are related to the acceleration?a, the initial position?x0?, and the initial velocity?v0

老外在語(yǔ)言描述方面還是非常講究的，舉個(gè)??：

Falling from a tower和Thrown down from a tower

第一個(gè)是從塔上掉下去，是沒(méi)有初速度的；第二個(gè)是刻意從塔上丟下去的，那么在這道題中的object就會(huì)有一個(gè)初速度

他們的書(shū)會(huì)把這道題涉及到的方方面面都講到：

The tangent is a straight line that touches the curve only at the one chosen point, without passing across or through the curve at that point.

delta?t?=?t 1-?t2 時(shí)間差

average velocity=v1-v2/t1-t2

The slope of a curve at any point on a graph is the slope of the tangent to the curve at that point. On a graph of position vs. time, the?slope?is equal to the instantaneous velocity. On a graph of velocity vs. time, the slope is the acceleration.

那總結(jié)差不多就到這里了，希望能幫到大家