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# Over a time interval of 2.16 years, the velocity of a planet orbiting a distant star reverses direction, changing from +20.9 km/s to −18.5 km/s. find (a) the total change in the planet's velocity (in m/s) and (b) its average acceleration (in m/s2) during this interval. include the correct algebraic sign with your answers to convey the directions of the velocity and the acceleration.​

• Réponse publiée par: jbaningzzz

Kepler’s laws of planetary motion, in astronomy and classical physics, laws describing the motions of the planets in the solar system. They were derived by the German astronomer Johannes Kepler, whose analysis of the observations of the 16th-century Danish astronomer Tycho Brahe enabled him to announce his first two laws in the year 1609 and a third law nearly a decade later, in 1618. Kepler himself never numbered these laws or specially distinguished them from his other discoveries.

Explanation:

Kepler’s three laws of planetary motion can be stated as follows: (1) All planets move about the Sun in elliptical orbits, having the Sun as one of the foci. (2) A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time. (3) The squares of the sidereal periods (of revolution) of the planets are directly proportional to the cubes of their mean distances from the Sun. Knowledge of these laws, especially the second (the law of areas), proved crucial to Sir Isaac Newton in 1684–85, when he formulated his famous law of gravitation between Earth and the Moon and between the Sun and the planets, postulated by him to have validity for all objects anywhere in the universe. Newton showed that the motion of bodies subject to central gravitational force need not always follow the elliptical orbits specified by the first law of Kepler but can take paths defined by other, open conic curves; the motion can be in parabolic or hyperbolic orbits, depending on the total energy of the body. Thus, an object of sufficient energy—e.g., a comet—can enter the solar system and leave again without returning. From Kepler’s second law, it may be observed further that the angular momentum of any planet about an axis through the Sun and perpendicular to the orbital plane is also unchanging.

• Réponse publiée par: elaineeee

Law of intertia

Explanation:

The question has an apsistance but instead of this i have an idea.

Equivalent force sould be equal to frictional force. Additionally we know that the frictional force direction is opposite direction of velocity. As a result we can easily see that if the bowling ball is on move, it will want going on. If it not, won't.

Have a good works..

• Réponse publiée par: hellcrack777

We can't buy prescription drugs over the counter without doctors prescription for safety purposes. Unlike paracetamol or other over the counter medicines, prescription drugs are highly dangerous when used wrongly that is why doctor's prescription is needed to serve as an evidence and a precautionary measure. An common example of prescription drug is sleeping pills, we cannot just directly buy it on pharmacies, it needs doctors prescription to prevent overdose or drug abuse.

• Réponse publiée par: homersoncanceranguiu

DENSITY, in short definition, is the degree of compactness of a certain object or substance. In science, we normally define it as the mass per unit volume.

density = mass / volume

Moreover, density is an INTENSIVE PROPERTY - the property of a material/object which does not depend on the mass of the object or its quantity; thus the density of an object is constant regardless of its mass or size.

SPECIFIC WEIGHT, on the other hand, is the weight per unit volume of a certain object/material. It is also called as the unit weight.

Specific weight = weight / volume

As opposed to density, specific weight is not constant.

Why?

Because as seen on its formula, its value is dependent on weight and volume. Even if we consider that volume is not affected by gravity, specific weight would still be affected using the weight.

Recall that weight is the body's relative mass being contained in the body which gives the downward force or we typically say how heavy the object/body is.

If we further use the formula in finding the weight, we have

weight = mass x acceleration due to gravity

w = m x g

Notice that if we are to use the formula, mass as constant, increasing or decreasing the value of the acceleration due to gravity would increase/decrease the value of the weight. Thus, an increase/decrease of the value of the weight would also further increase/decrease the value of the specific weight.

Therefore, the density does not change in different gravity, but the specific weight does.

For more related topics, see links below.

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Over a time interval of 2.16 years, the velocity of a planet orbiting a distant star reverses direct...