英文物理题,高手们,帮帮忙吧~跪谢了!!

麻烦翻译一下题, 然后能否给出用英语回答的答案...拜托!! 谢谢!!
1.Define either kinetic energy or potential energy.

2.what's power and what are the SI units for power?

3.what are the four phases of matter?

4.what is the density?

5what is pressure?

6.A block slides to the right on a horizontal floor. in what direction is the force of friction exerted by the floor on the block? what is the reaction force (Newton's Third Law pair) to this force of friction? In what direction is the reaction force?

7.the net force on a 5kg block is measured to be 10N. what is the acceleration of the block?
8.A 4kg block is heading toward a head-on collision with 2kg block. If the 4kg block has a speed of 3m/s just before the collision and the 2kg block is at rest, what is the speed of both block if they collide and stick together?

1.Define either kinetic energy or potential energy.
1 给动能和势能下定义
ANSWER:
(1) The kinetic energy stands for the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity.
(2) The potential energy is defined as the energy that stored in an object or a system due to its position in a force field or due to its configuration.

2.what's power and what are the SI units for power?
2 什么是功率，国际单位制的功率是什么？ SI units是SYSTEM INTERNATIONAL UNITS 国际单位制
ANSWER:
(1) Power is the rate at which work is performed or energy is converted
(2) The SI units for power is Joule.

PS Joule是焦耳热

3.what are the four phases of matter?
3 事物的四态是什么

4.what is the density?
4 密度是什么？
ANSWER:
The density is an intensive property which is defined as an object's mass over its unit volume. The symbol of density is ρ.

5.what is pressure?
5 什么是压力？
ANSWER:
The pressure 'P' is the force per unit area applied in a direction perpendicular to the surface of an object.

6.A block slides to the right on a horizontal floor. in what direction is the force of friction exerted by the floor on the block? what is the reaction force (Newton's Third Law pair) to this force of friction? In what direction is the reaction force?
6 一个木块在水平地面向右滑行，问由地面对木块施加的摩擦力的方向。 这个摩擦力的反作用力是什么（根据牛顿第三定律），反作用力的方向是什么？
反作用力是木块施给地面的摩擦力，方向水平向右
ANSWER:
The direction of the force of friction on the box is to the left.
The reaction force is the force that exerted by the block on the floor. Its direction is right.

7.the net force on a 5kg block is measured to be 10N. what is the acceleration of the block?
7 一个5公斤重的木块净重为10牛。求物体的加速度
ANSWER
According to Newton's second law F=m*a where F is the force, m represents the mass. So a=F/m=10N/5kg=2m/s^

(^代表“平方”)

8.A 4kg block is heading toward a head-on collision with 2kg block. If the 4kg block has a speed of 3m/s just before the collision and the 2kg block is at rest, what is the speed of both block if they collide and stick together?
8 一个4公斤重的木块朝着一个2公斤重的木块迎面相碰。如果4公斤重的木块在碰撞前速度为3米/秒，而2公斤重的木块为静止，如果他们相碰后连在一起滑行，问速度是多少？
解题思路动量守恒定理
ANSWER:
According to the momentum theorem, Since momentum is always conserved, the sum of the momenta before the collision must equal the sum of the momenta after the collision. Therefore we have: 4kg * 3m/s + 2kg * 0m/s=(4kg+2kg)*v
So v=2m/s is the answer.

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