Question 1: How is acceleration caused if
not by an unbalanced force?
Ethan: I just came from another physics site that discussed Newton's laws. They said his 1st law states that an object's acceleration is due to an unbalanced force. Are you saying here that there is no such thing as an unbalanced force? How do you think an object can possibly accelerate if it is not being pushed in some direction by an unbalanced force? I'll go with Newton on this one. W. J. Lincoln City, OR, USA
Question 2: Why does gravity behave so
forcefully at times?
Hi Ethan: I am enjoying your articles. Keep them coming. My question is about gravity. Most times it seems easy to handle. But at other times, the force of gravity can be brutal. Like when I was younger and fell from a ladder and hit my head on a sidewalk. I'll never forget how violent that blow felt to my head. I didn't black out, but it was some time before I felt okay. Why does gravity behave so forcefully at times like this and not at others? R.S. Austin, TX, USA
Question 3: Would a
non-rotating Earth still bulge?
Good morning Sir: I was wondering if the earth's rotation were halted and instead all other objects in the universe rotated the other way around earth's axis at the rate of one rotation every 24 hours, do you know if the earth would continue to maintain the bulge around its equator? rhanson
Question_4: Does A.C.E. disprove the a/R
force of matter?
Hello: Have you visited the A.C.E. spacecraft web site at http://sd-www.jhuapl.edu/ACE/ACE_FactSheet.html ? This spacecraft is in a halo orbit of the Lagrange L1 point where it generally stays in line between the earth and the sun throughout the year. The fact sheet lists the spacecraft's position as follows.
"ACE will orbit the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth and 148.5 million km from the Sun."
Notice how the gravitational forces are in equilibrium, meaning the spacecraft is attracted to the sun by a gravitational force that is equal to the gravitational force the spacecraft is attracted in the opposite direction to the earth. My question is that if this event is occurring as you predict, with the ACE spacecraft accelerating in the sun's direction as it orbits the sun, then are you not predicting that your acceleration/Reaction force is reacting on the spacecraft's matter in the earth's direction? If so, I wonder if your a/R force is not an extra, unnecessary outward force, which if it did exist, would upset the balanced state of the spacecraft's current gravitational equilibrium which is the obvious reason the spacecraft is able to maintain its position at the L1 point throughout the year?
Is centrifugal force real?
Ethan: I think centrifugal forces are real. Do you agree? If so, then why are we being told by the experts that they are false or imaginary? E.R., Mexico City, Mexico.
Additional thoughts on the confusion surrounding accelerating frames of reference.
Question 6: What is kinetic energy's role during
Ethan: If you are correct in saying that kinetic energy is imaginary, then how do you explain the heat being generated by the application of a moving car's brakes? Is not the car's stored kinetic energy being converted into heat energy as the car's speed is being reduced? mkleist, Bonn, Germany
Question 7: What is curved space?
Ethan: Please explain curved space. Brett W., Boston, Massachusetts, USA
What causes Earth's dual high tides?
I have read that the greater high tide on the moon side of the earth is caused by attraction of the water toward the moon while the lesser high tide on the opposite side of earth is caused by that water lagging behind in earth's acceleration around the center of mass it shares with the Moon. I think this comes from Newton's theories. Do you think this is the correct cause of these high tides? Walter E., Vancouver BC, Canada.
Will you help me fill in the blanks?
Please help me fill in the blanks
1. a body at rest tends to --------- at rest
2. a body in motion tends to -------- in motion
3. For every action there is an ---------and------------ re-action
Thank you, E.B., Weston, Ontario, Canada
Question 10: The direction of the
pendulum's overall force is... ?
The Pendulum Event
The following survey question was asked of the physics students of several colleges. The results of the survey caused the survey's author great concern since the students, more often than not, failed to give the expected answer. An article on the results by the survey's author was printed in a well-known physics magazine. The magazine received several letters challenging the validity of the expected answer. The author defended his position with apparent success. Since I still disagreed with the expected answer, I decided to submit an analysis to the magazine. My analysis included a drawing of the event. Overall my submission was the opposite of brief. The magazine's editor politely explained that he could not print my analysis of the pendulum event due to the lack of space.
The Survey Question
A swinging pendulum bob is, for a brief instant, directly below its point of support. Draw an arrow indicating the direction of the overall force on the bob at this instant.
The Expected Answer
The student draws an upward-directed arrow over the bob in the direction of its support.
Question 11: Is not inertia the reason for objects's same rate-of-fall?
After reading the first article about inertia, I have uncovered a problem. I learned in school some time ago that different sized objects fall at the same rate for the following reason: a more massive object has more inertia that needs to be overcome so its greater weight is no more effective in causing acceleration than is the lesser weight of a less massive object with its lesser inertia. The problem is that now that I understand that inertia is a standin for the acceleration/Reaction force of matter, and as such could never be the cause of any event, I am left unsure as to the reason why objects fall at the same rate here on earth. Do you have the answer? J. T., Dallas, Texas, USA.
Do Newton's laws hold true in accelerating frames?
It seems to me that Newton's Laws are not the whole answer since they only hold true in frames where acceleration is absent. After reading through your site, I get the feeling that you think otherwise. If so, please explain why. J.W., Boston, MA, USA
How wrong is the bowling ball-rubber sheet model?
I often read of the following demonstration of the space-time theory of gravitation. A bowling ball, representing the sun is placed on top and in the middle of a horizontally stretched sheet of rubber. The weight of the bowling ball causes a circular depression to form. A marble, representing the earth, is set into motion around the stationary bowling ball. It is then pointed out that the earth marble ends up orbiting the sun bowling ball as if there exists some imaginary gravity force between them that is pulling the earth marble in the direction of the sun bowling ball.
After reading through several articles on Universal Physics, I have a pretty good idea of what you think of the space-time theory. What I am really wanting to know is if you see anything wrong with this bowling ball resting on a rubber sheet model.
W.G., Philadelphia, PA, USA
Is centrifugal acceleration real?
Dear Mr. Skyler:
I have read with interest your descriptions of centripetal force and centripetal acceleration. I agree that centrifugal force is a real acceleration/Reaction force. I wonder if centrifugal acceleration is also real. On another site where the Coriolis force is explained, centrifugal acceleration is said to be possible since it is apparent to an observer who is riding on the earth's rotating surface. They say the object being observed is experiencing centrifugal acceleration and further that its cause is an apparent force predicted to be present by Newton's law 1. This force they refer to as the Coriolis force. No further explanation is offered as to the nature of this force nor its cause. Will you look into this and let me know if you think centrifugal acceleration is real or not?
F.W. (no city or country indicated)
Quarter mile drags + lightened flywheel = improved times. Why?
I have been thinking about momentum and inertia and the accepted science around these topics as well as the questions posed by your articles. Here is something I would like to see explained. Take any road car and measure its performance over a quarter mile. Remove the spare wheel or otherwise take 15 lb. out of the car and measure the performance again. It may be faster but the difference will be insignificant. Now lighten the flywheel by 15 lb. and measure the car's performance times again. The car is faster and not by the amount of weight removed from the flywheel it is measurably faster. What is at work here?
There is another situation with the light and heavy flywheel. In quarter mile drags if the same start manner is used by revving up to the limiter and dropping the clutch with the light and heavy flywheels the car with the heavy flywheel will get off the line faster but will be caught and beaten by the car with the light flywheel. Of course we assume identical cars with the same power to weight ratio. The heavy flywheel is also more likely to burn clutches and break drive train parts coming off the line. This must have something to do with the heavy flywheel at high rpm when the clutch is dropped. If inertia and momentum are not responsible, then what is causing the damage?
R.M., Thornhill, South Africa
Question 16: Web discussions of Universal Physics?
Can you direct me to any discussions of Universal Physics on the web? I am enjoying what I have read so far but am wondering what others think.
J.U., British Columbia, Canada.
I recently found a You Tube video titled "Misconceptions About Falling Objects" produced by Veritasium in which the interviewer was asking students to consider a test where two balls of different weights were dropped at the same time from the same height. Most students interviewed thought that both balls would reach the ground at the same time which I think is correct. But he went on to question why this was so considering that the heavier medicine ball had the greater gravitational force. The interviewer then gave his opinion that the heavier ball had a lot more mass which meant that it had a lot more inertia which he said was a "resistance to acceleration". I think he is telling us that due to the resistance force of inertia the greater force of the medicine ball's gravity is unable to cause anything more than the normal rate of acceleration of the lighter basket ball. Is his inertia explanation correct?
G.D., Cedar Falls, IA, USA
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