# acceleration due to gravity

## speeding up while falling down

Gravity is a force that pulls objects down toward the ground. When objects fall to the ground, gravity causes them to accelerate. Acceleration is a change in velocity, and velocity, in turn, is a measure of the speed and direction of motion. Gravity causes an object to fall toward the ground at a faster and faster velocity the longer the object falls. In fact, its velocity increases by 9.8 m/s2, so by 1 second after an object starts falling, its velocity is 9.8 m/s. By 2 seconds after it starts falling, its velocity is 19.6 m/s (9.8 m/s + 9.8 m/s), and so on. The acceleration of a falling object due to gravity is illustrated in the Figure 1.1. Q: In this diagram, the boy drops the object at time t= 0 s. By t = 1 s, the object is falling at a velocity of 9.8 m/s. What is its velocity by t = 5 s? What will its velocity be at t = 6 s if it keeps falling? A: Its velocity at t = 5 s is 49.0 m/s, and at t = 6 s, it will be 58.8 m/s (49.0 m/s + 9.8 m/s).

## mass and acceleration due to gravity

What if you were to drop a bowling ball and a soccer ball at the same time from the same distance above the ground? The bowling ball has greater mass than the basketball, so the pull of gravity on it is greater. Would it fall to the ground faster? No, the bowling ball and basketball would reach the ground at the same time. The reason? The more massive bowling ball is also harder to move because of its greater mass, so it ends up moving at the same acceleration as the soccer ball. This is true of all falling objects. They all accelerate at the same rate due to gravity, unless air resistance affects one object more than another. For example, a falling leaf is slowed down by air resistance more than a falling acorn because of the leafs greater surface area. Q: If a leaf and an acorn were to fall to the ground in the absence of air (that is, in a vacuum), how would this affect their acceleration due to gravity? A: They would both accelerate at the same rate and reach the ground at the same time.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

a heavier object always falls to the ground more quickly than a lighter object.

``````a. true

-->  b. false
``````

what is the velocity of an object that has been falling freely in a vacuum for 4 seconds?

``````a) 9.8 m/s

b) 10.1 m/s

c) 19.6 m/s

-->  d) 39.2 m/s
``````

objects fall toward earth at a constant rate of speed.

``````a. true

-->  b. false
``````

an object will experience more air resistance when it falls if it has greater

``````a) mass.

b) weight.

c) gravity.

-->  d) surface area.
``````

objects with different masses have the same gravitational force acting on them.

``````a. true

-->  b. false
``````

## diagram questions

No diagram questions associated with this lesson