Gravity Review Sheet Answers: Review: Gravity Whenever we tell how fast or slow something is going, we tell how far the object will move in a given time, such as miles per hour or meters per second. This is called the object’s speed. When we also tell in which the direction the object is traveling, we now refer to its movement as its velocity. How much this changes over time, whether it is an increase or decrease, is known as the object’s acceleration. For example, for a falling object in a vacuum, it is 9.8m/s/s. Mass and weight are not exactly the same. Mass refers to the amount of matter in an object, while weight is a measure of gravity on the object. In the metric system, weight is expressed in newtons while mass is expressed in kilograms. In ancient times, the famous Greek philosopher Aristotle stated that heavy objects fall faster than lighter objects. This idea was finally questioned by the Italian scientist Galileo,, who said that in a vacuum (to avoid air resistamce), all objects will fall at the same rate. He proved this by using weights tied to a string that he would swing back and forth. This device is called a pendulum. In the experiments we did in class, we discovered that the only variable which affects the period of a swinging object was the length of the string. In 1665, another scientist, Isaac Newton, was supposedly sitting under a tree and watched an apple fall, and while looking at the moon in the sky at the same time, started thinking about the force of gravity. He came up with the Law of Universal Gravitation, which stated that the force of gravity between any two objects depended on the mass of the two objects and the distance between them. To calculate how fast objects fall, you use the following equation: Δv = g x t For example, if you went up to the top of Frost’’s roof above the gym and dropped a penny down to the basement level, let’s say it would take 1.5 seconds. What would the penny’s velocity be as it hit the ground? (you wrote what g is, the acceleration of gravity, on the first page of this review) 14.7m/s Objects will not keep speeding up forever as the air slows a falling object. When air finally prevents a falling object from accelerating, we say that the object has reached its terminql velocity. is the condition of an object which is falling with no other Free fall force slowing it down. This is impossible on the earth because of the atmosphere. Objects that are in orbit are experiencing this condition. Astronauts seem to float, but they are really falling around the earth. If it were not for gravity, a satellite launched horizontally would go straight (into space) instead of in an orbit. Gravity, since it causes the satellite to move in a circle around the earth, is called a centripetal force. Since gravity decreases as you move away from the earth, satellites orbiting the earth do not need to go as fast in their orbit as they get further and further away. The International Space Station, in low earth orbit, travels at a rate of about 5 miles per second; geosynchronous satellites, which orbit with the earth’s rotation, take 24 hours to circle the earth, while earth’s natural satellite, the moon, takes about a month to go around the earth once. When an object is falling as it is traveling in a horizontal direction, it travels in a curved path; we refer to this as projectile motion. Even though traveling, falling objects may be moving fast (such as a shot bullet), they still fall at the same time as an object that has no horizontal velocity-gravity “doesn’t care” if an object is moving or not. All objects, including you, have a point where the mass of the object is concentrated. We call this the center of gravity. For a regular object, this point is usually in the middle of the object, whereas for an irregular object, it could be located just about anywhere. For an object to properly balance (not fall over), this point of an object must be close to the ground and above its base.
Pages to are hidden for
"Gravity Review Sheet Answers:"Please download to view full document