# Gravity Is Acceleration

Gravity Is Acceleration

Gravity is one of the 4 forces in the Universe. Although it is the weakest force, it is the most important since it controls the fate of time, space, and ultimately matter (you are made of matter and live in time and space!). Galileo, overturning Aristotle’s false and widely held assumption that heavier objects fall faster to Earth,discovered thatgravity was a force that accelerated objects equally to the Earth no matter their differences in mass. Newton described the motions of falling bodies well enough to understand the trajectory of a falling rock, a spaceship or a planet. And Einstein explained how gravity controls the expansion of the Universe as well as the fabric of space and time.

1. At the surface of the Earth gravity accelerates all things towards the Earth at a rate of 9.8 m/s2. That means a rock dropped from above the Earth will fall faster as it approaches the ground. If a rock falls for 10 seconds before it hits the ground, what is its speed when it hits the ground?

But gravity weakens as we travel away from Earth. At the height of the International Space Station in low Earth orbit, gravity is only about 90% the strength at Earth’s surface.

2. What is the rate that an object would fall at inside the ISS?

(hint: multiply 9.8 m/s by 0.9)

3. If you drop a rock inside the ISS and it falls for 10 seconds how fast is it going when it hits the floor?

If we graph the affect of gravity on a falling object on a graph of distance versus time we get a curved line because the object is accelerating. But if we graph the same object falling by speed versus time we get a straight line because the object is accelerating continuously. Be careful when reading graphs!

Make a graph on the back of this page of time vs. speed for a falling object and at each data point on the graph write the distance it has travelled for each second.

Time in seconds / Speed in m/s / Distance in meters
0 / 0 / 0
1 / 10 / 10
2 / 20 / 30
3 / 30 / 60
4 / 40 / 100
5 / 50 / 150

Label and number your graph carefully and completely! Time goes on the x axis. Label each second every 5 lines. Speed in m/s goes on the y axis. Label 10m/s every 5 lines.

a. How far has the object fallen in 1 second?

b. How far has the object fallen in 2 seconds?

c. How far has the object fallen in 3 seconds?

d. How far has the object fallen in 4 seconds?

e. How far has the object fallen in 5 seconds?

f. Do heaver objects fall faster than light objects?

g. What is the rate that all objects fall to Earth in m/s due to the force of gravity?