Term-1 physic讨论区

树熊123

小弟在此开一个term-1的物理讨论区
如题，有什么关于物理的问题一起进来讨论，研究

P/S：单身妹子无任欢迎<<<被拖走

weston123453

你好哦,请问你们教到哪里了?我是14/15  batch的.感觉我们老师教很快

doeramon

weston123453 发表于 29-5-2014 12:23 AM
你好哦,请问你们教到哪里了?我是14/15  batch的.感觉我们老师教很快

我的老师教到第二课
老师肯定要教快的，不然怎么教完11课

树熊123

doeramon 发表于 29-5-2014 09:46 AM
我的老师教到第二课
老师肯定要教快的，不然怎么教完11课

我们的老师最近比较忙，所以我们自修
我自己是读到第二课

weston123453

.....wa你们都好快,我的老师才教完第一课......我会以为快是因为另外一班才教到第一课vector(scalar&cross product 还没有教...)那边 我是自己读完第二课咯现在....

doeramon

1)The magnitude of a force whose two components are perpendicular to each other is 40N. One component has magnitude 20N. Determine
a)the magnitude or the second component, and
b)the angle between the 40N force and the second component

2)A 30N force F has two components which are perpendicular to each other.Determine
a) the magnitude of these components if the magnitude of one is twice as larger as the other
b) the angle between F and the larger component

weston123453

doeramon 发表于 29-5-2014 04:44 PM
1)The magnitude of a force whose two components are perpendicular to each other is 40N. One componen ...

answer?

doeramon

weston123453 发表于 29-5-2014 04:55 PM
answer?

1）a)34.6N
b)我不懂答案
2)a)y=26.8N,x=13.4N
b)26.7

hhm1388

第二题方法一样我就不重复了

weston123453

doeramon 发表于 29-5-2014 05:09 PM
1）a)34.6N
b)我不懂答案
2)a)y=26.8N,x=13.4N

.

weston123453

coefficeint of static friction 是拿来算什么的哦?

树熊123

weston123453 发表于 30-5-2014 01:03 AM
coefficeint of static friction 是拿来算什么的哦?

coefficient of static friction是静摩擦因数。把静止的物体拉到运动起来时所需的最大力=静摩擦因数*压力。
coefficient of static friction 是用来算limiting frictional force,即把静止的物体拉起来所需的force.

不懂对不对

weston123453

chapter1不会==
请问那个graph我们要找它的数值时,应该放几个significant figure或decimal places
example:
那个logv or log lambda 要放几个s.f or 几个d.p?

doeramon

1)The length of a cube L= (3.50+-0.05)cm. The volume of the cube V should be written as
ans: V=(43+-2)cm^3
为什么不是放3个s.f?

2)The period T of the vibration of a load at the end of a vertical spring depends on the mass m of the load and the force constant k of the spring .Use the method of dimension to derive an equation relating T with m and k
ans:T =Cm^x k^y
T= M^x(MLT^-2/L)^y
这只是部分步骤
我加深的字： 为什么要放L?k 的dimension不是MLT-2罢了吗？

p/s: 字体较小的就是power

3)unit 是N的时候要放多少位数？oxford 书的m/s 25 第6题，要怎样知道放几个位数？

weston123453

doeramon 发表于 7-6-2014 09:20 PM
1)The length of a cube L= (3.50+-0.05)cm. The volume of the cube V should be written as
ans: V=(43 ...

1)后面absolute error 要1s.f
   .然后前面的value 就要 follow 那个1s.f 的absolute error 的decimal place

2)是FORCE CONSTANT 不是force

3)

weston123453

请问谁可以来答我的问题！！！

doeramon

weston123453 发表于 8-6-2014 02:11 AM
1)后面absolute error 要1s.f
   .然后前面的value 就要 follow 那个1s.f 的absolute error 的decimal p ...

2)force constant是什么formula?
3)8cos 30' -(6sin 40'+5cos 55')=0.204N
怎样知道放几个d.p?

TALL

doeramon 发表于 8-6-2014 10:25 AM
2)force constant是什么formula?
3)8cos 30' -(6sin 40'+5cos 55')=0.204N
怎样知道放几个d.p?

除了算uncertainty之外，其他的calculation 如果不详的话，放3个s.f. 为佳。

doeramon

1)A bullet is fired horizontally from the top of a cliff on the surface of the earth with a speed of 40ms^-1 . Assuming no air resistance, what is the speed of the bullet 3s later?
ans: 50ms^-1

2) A projectile leaves the ground at an angle of 60' to the horizontal .Its initial kinetic energy is k. Neglecting air resistance, find in the terms of K its kinetic energy at the highest point of the motion
ans: 1/4 K

怎样做？

weston123453

doeramon 发表于 11-6-2014 10:25 AM
1)A bullet is fired horizontally from the top of a cliff on the surface of the earth with a speed of ...

接下来的那题不明白它的意思勒。。。。。highest point of motion not means the velocity is equal to 0?