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Newton’s First Law Sir Isaac Newton

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Newton’s First Law Sir Isaac Newton
Name: _______________________________
Newton’s First Law
Sir Isaac Newton
Sir Isaac Newton is one of the most influential scientists of all time. He came up
with numerous theories and contributed ideas to many different fields including
physics, mathematics and philosophy. Born in England, Isaac Newton was a
highly influential physicist, astronomer, mathematician, philosopher, alchemist
and theologian.
One of Newton’s biggest scientific contributions came from three very basic laws
which we refer to as Newton's three laws of motion. Our first focus starts with
Newton's first law of motion - sometimes referred to as the law of inertia.
The 1st Law
Newton's first Law of Motion is often stated as:
An object at rest stays at rest and an object in motion stays in motion with the same speed and in
the same direction unless acted on by an unbalanced force.
There are two parts to this statement
1. One predicts the behavior of stationary objects
2. The other predicts the behavior of moving objects.
Let’s say the object is at rest. Unless something makes it move, it will just sit there (kind of a “duh”
statement isn’t it?). It’s similar for something that is moving. Unless something gets in the way of the
moving object, it will just keep on moving in the same direction and at the same speed.
Simply put, the behavior of all objects can be described by saying that objects tend to "keep on doing
what they're doing.” So if they are at rest, they will stay that way. If an object is in motion with an
eastward velocity of 5 m/s, they will continue in this same state of motion (5 m/s, East). If an object is in
motion with a leftward velocity of 2 m/s, they will continue in this same state of motion (2 m/s, left).
Inertia
In fact, it is the natural tendency of objects to resist changes in their state of motion. If they are stopped,
they don’t want to move. If they are moving, they don’t want to stop. This tendency to resist changes in
their state of motion is described as inertia.
Inertia: the resistance an object has to a change in its state of motion.
1. Describe an example of something that’s hard to get started moving, but once it gets moving, it’s hard
to stop.
___________________________________________________________________________________
2. Describe what happens to an object in each of the following scenarios:
a. Let’s start with an easy one. A penny is sitting stationary on a card.
The card is pulled from under the penny. Describe what happens
and why to the penny:
b. A car is making a right turn and the driver side door suddenly
opens. What happens to the driver who for some illegal
reason wasn’t wearing a seatbelt and was sitting on a freshly
cleaned, slippery leather seat? Why?
Unit 2: Relative Motion
77
c. An elevator’s cable breaks and begins falling to the ground. The passenger jumps
out the open elevator door at the last second landing safely on the ground. What’s
wrong with this scenario? Why?
Homework – RELATIVE MOTION – Day #2
Name: ____________________
Period: _____Date: __________
1. A wide river f ows from North to South at a steady rate of 2 m/s. T e motor boat has
been tested on a calm pond and it was found that it goes through the water at 8 m/s.
3. A wide river flows from North to South at a steady rate of 2 m/s. The motorboat is traveling along at 8
m/s.
a. What is the velocity of the boat relative to the inner tube?
V
current = 2 m/s
a) During a 5-second period how much distance does
the boat move over the water as seen by the person
b.in the
What
is the
velocity of the boat as seen from the bridge?
inner
tube.
____________________
c. What is the velocity of the inner tube as seen from the
b) Find
the boat’s displacement as seen by the observer
bridge?
watching from the bridge for 5 seconds.
____________________
d. If the boat cuts off its engine,
what is the velocity of the boat
with respect to the inner tube?
c) What is the velocity of the boat relative to the inner
tube?
e. If the boat restarts its engine (traveling again at 8 m/s) and
____________________
the driver jumps in the air out of joy, where does the driver
land?
d) What is the velocity of the boat as seen from the
bridge?
Figure 2.26
____________________
e) What is the velocity of the inner tube as seen from
the bridge?
____________________
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