Physics help! I am having an argument with a friend and I need to prove this point.?

Question

In the first law of motion by Issac Newton it says that if something
is moving in constant motion then it is considered straight movement because if you were to put it on a graph it is linear.
So if an object is moving in constant motion or in the same way without interferance then it is straight right.My friend says that the
object HAS to travel in a straight line for it to be straight.Me I
just said that the velocity has to be good and that even if a object
is going in a circle and the speed is constant it can apply.So
he is saying that in the first part of the Law when Issac says
that an object in motion will stay in motion or in a constant way
or constant speed in a straight line does it mean straight line
as in it literally goes straight or its speed is constant and
it can go in a circle?

I might not be correct so please tell me if I am right or wrong.

Wait so its the force and not if like a spaceship were to travel the same speed
and stuff and yet turn.

If it had the variables changing it from the beginning of a movement is it not
constant though.And it stayed the same
speed.

Answer 1

Newton's first law of motion is often stated as

An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Newton clearly stated that it should stay in the same direction. However, when it comes to circular movement, there are 3 forces which are acting on an object. Two of these forces balance each other. One of them is towards the center and the other out from the center all the time. The third force is perpendicular to the axis of these two forces.

Now lets see again what Newton has said:

An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Here Newton is saying "unless acted upon by an unbalanced force." In circular movement, there are three forces acting on the object however two of them are balanced. Since there is only one remaining force with constant magnitude on the object, it stays in motion with the same speed in the same circular direction. Therefore we can say that Newton's 1st Law is true for Circular movement. Although his rule is valid for circular movement, Newton didn't state it in aware of circular movement.

Answer 2

Considering Newtonian physics only (which you are), the object will move in a straight line at constant velocity unless acted upon by an external force. This HAS to be in a straight line.

If the object is going in a circle then it has an external force acting on it. In the case of an orbitting spacecraft or a planet orbitting the sun (where there isnt anything physically attached to it pulling or pushing) the force is obviously the gravitational force between the "two" objects.
An object which is travelling at constant speed in a circle is having a force on it which is pointing directly into the centre of the rotation.

Answer 3

Unless an object is acted on by an external force, its vector should stay the same. That includes its direction. An object will only turn when acted on by an external force. The motion of the Earth around the Sun is not actually a curved vector, but two linear vectors combined. The Sun's gravity is constantly pulling the Earth in, but the Earth's high tangental velocity parallel to the sun keeps it from falling into the Sun. The Sun's gravity is the external force that turns the Earth and keeps it in the Solar System.

Speed is not the same as velocity. Velocity is speed and the direction that speed is acting in.

Objects will not turn unless acted on by an external force, but the centrifugal force you feel, when in a turning car for example, is actually inertia, the same thing that keeps moving things moving and stopped things stopped.

Answer 4

The fist law means that the velocity will remain the same unless there is a net force acting. Forget the speed.

Changing direction means changing velocity, even if the speed stays the same. So the object can only deviate from moving in a straight lineif a force acts - your friend is correct.

Answer 5

Newton's first law states basically that an object in motion tends to stay in motion, and an object at rest tends to stay at rest. The key point is that there is an absence of an external force. Physics considers circular motion to be accelerated or "changing" motion, and an external force of some sort needs to be present, or the object will not continue in a circle. So the law doesn't apply...

Answer 6

Issac Newton meant straight as in a straight line. But he didn't know what Einstein knew. Space Time can warp and curve.

If space itself curves then from the point of view of an outside observer, the object will not travel straight even though the net force on it may be zero. From the perspective of the object, as long as not net force is applied to it, it does travel straight.

So it's more correct to say, that an object set in motion will travel in a straight line relative to space-time as long as no net force is acting on it.

Answer 7

The wording of Newton's first law is clearly directed toward straight line motion. But that's simply because Newton hadn't gotten to circular motion yet. In Newton's original wording, curved motion requires a force input, since conservation of momentum would otherwise dictate straight-line motion.

But, Newton's law DOES also applies to circular motion. That's what keeps the Earth spinning and only gravitational dragging by the Moon is causing the Earth's rotation to slow down.

Answer 8

an object will continue moving in a straight line with constant velocity unless acted upon by an outside force. velocity is speed and direction so if an object is following any type of curve (direction of motion is changing) then it does not have a constant velocity and is being acted on by a force.

Answer 9

It will move in a straight line. Any time an object changes direction, it is because another force is acting on it, altering the vector in which it travels. An object acting entirely on its own (except for some sub-atomic particles which Newtonian physics doesn't address) will not change direction or speed without outside interference.

Answer 10

even as it comes precise all the way right down to it, the only guidance that any faith has that it really is perfect, and all different religions are incorrect are what it says some e book, and the information of yet another those who study that e book and positioned on humorous clothing. inspite of in case you insist that the guidance of the universe round us demands that there be a author (i do not agree, yet it really is yet another argument), there is unquestionably NO guidance in besides that the author is the in basic terms that takes position to be worshipped by technique of X faith. So no, Pascal's wager, the watch contained contained in the woods, and so on. can in basic terms as actually be used as guidance for Scientologists, Raelians, Norse mythology, or that Raven made the Earth from turtles and airborne dirt and airborne dirt and dust as they are able to to assist the Christian Genesis fantasy.