An object is thrown up with an initial speed [图],...

A.Error

B.Event

C.Object

D.Exception

E.Throwable

F.RuntimeException

An object moving in r =100m circle satisfies:, how much is the magnitude of acceleration when t=1s?

An object moving in r =100m circle satisfies:, how much is the magnitude of acceleration when t=1s?

The main purpose of Paragraph 2 is to ______.

A．answer an objection that some readers may raise to Paragraph 1

B．guard against the possibility that you have read Paragraph 1

C．contradict the idea of Paragraph 1

D．show more optimistic than Paragraph 1

A.x.delete（）

B.x.finalize（）

C.Runtime.getRuntime（）.gc（）

D.Explicitlysettingtheobject’sreferencetonull.

E.Ensuringtherearenoreferencestotheobject.

F.Onlythegarbagecollectionsystemcandestroyanobject.

When an object receives a（ ）, methods contained within the object respond.

A.parameterB.informationC.messageD.data

In 1908, an object from outer space devastated2,000km2of forest in Siberia. The object was between10m and 100m in diameter and traveled at a maximumspeed of 15km/sec. It exploded at an altitude of 8km andreleased energy equivalent to 20million tons of TNT. Twoscientists discuss whether this object was a comet or anasteroid.

Scientist 1

The object was a comet, a body made of ices (such asfrozen water or methane) and dust. Most of this cometarymaterial is volatile(easily vaporized) and low in density.Friction in Earth’s atmosphere heated the comet to a tem-perature at which it exploded, high above the ground. Themajority of the ices and dust were vaporized in the explo-sion, which explains why no crater was formed at the siteand why no large, identifiable fragments of the object werefound. An asteroid would not have been completelydestroyed. Intact asteroid fragments that reached theground would have created one or more craters uponimpact and left behind recoverable pieces. Evidence showsthat the object decelerated rapidly before it exploded.Because of their low density, comets are capable of suchrapid deceleration, whereas high-density objects, such asasteroids, are not.

Scientist 2

The object was a stony asteroid. As it entered Earth’satmosphere, its high speed created a large air pressure dif-ference between the area just in front of the asteroid andthe area just behind the asteroid. The large pressure differ-ence eventually exceeded the structural strength of theasteroid. The asteroid flattened, decelerated rapidly due tothe dramatic increase in its surface area, and fragmentedbefore reaching the ground. This fragmentation would haveappeared like an explosion. Calculations show that a cometbetween 10m and 100m in diameter would explode at analtitude much higher than 8km, but a stony asteroid of thatsize would fragment at or near an altitude of 8km.Recovery of large asteroid fragments is difficult due to thearea’s boggy soil; however, small, glassy fragments wererecovered and are believed to be melted and resolidifiedpieces of the asteroid.

Which of the following phrases best describes the majorpoint of difference between the 2 scientists’ hypotheses?

A.The location of the event

B.The speed the object was traveling

C.The density of Earth’s atmosphere

D.The type of object that entered Earth’s atmosphere