一道英文物理题A 4kg body is placed on horizontal ground.The coefficient of dynamic friction between the body and the ground is 0,2.The object is acted upon by a force of 30 N that encloses an angles of 20 whith horizontal.Find the friction for

一道英文物理题A 4kg body is placed on horizontal ground.The coefficient of dynamic friction between the body and the ground is 0,2.The object is acted upon by a force of 30 N that encloses an angles of 20 whith horizontal.Find the friction for
一道英文物理题
A 4kg body is placed on horizontal ground.The coefficient of dynamic friction between the body and the ground is 0,2.The object is acted upon by a force of 30 N that encloses an angles of 20 whith horizontal.Find the friction force and the acceleration of the body.

一道英文物理题A 4kg body is placed on horizontal ground.The coefficient of dynamic friction between the body and the ground is 0,2.The object is acted upon by a force of 30 N that encloses an angles of 20 whith horizontal.Find the friction for
翻译:一个4kg的物体放置在水平面上.物体和地面之间的摩擦因数是0.2.物体受一个与水平面夹角是20度的力的作用,力大小是30N.求摩擦力和物体的加速度.
竖直方向上物体没有加速度,受力平衡:
Fsin20度+N=mg 其中,F是拉力,N是支持力,令g=9.8m/s^2
f=μN f是摩擦力,解出:f=μ(mg-Fsin20度)=5.83N
水平方向上有加速度a.则根据牛顿第二定律:Fcos20度-f=ma
解出:a=5.59m/s^2
In the vertical direction,the body doesn't have acceleration:
Fsin20+N=mg,
F is the force that act upon the body,N is the force of support from the ground.Let g be g=9.8m/s^2
f=μN,
f is the friction force,μ is the coefficient of dynamic friction between the body and the ground.
So,f=5.83N
In the horizontal direction,according to Newton's Second Law:(Fcos20-f)=ma
a is the acceleration.
So,a=5.59m/s^2

楼上的翻译的已经很准确了
题目也应该不难的.

frictional force
0.2*(4*9.8-30*Sin20)
= 5.8 N
acceleration
(30*Cos20-0.2*(4*9.8-30*Sin20))/4
= 5.6 m/s^2

一4Kg的物体置于水平地面上。物体和地面之间的动摩擦系数为0.2。与水平线成20°角、大小为30N的力施于改物体上。求摩擦力和物体加速度。
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当该力是向上时，有：
G＝mg
F⊥＝F·sinα...

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一4Kg的物体置于水平地面上。物体和地面之间的动摩擦系数为0.2。与水平线成20°角、大小为30N的力施于改物体上。求摩擦力和物体加速度。
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当该力是向上时，有：
G＝mg
F⊥＝F·sinα
F‖＝F·cosα
G＝N＋F⊥，N＝mg－F⊥＝mg－F·sinα
f＝μN＝μ·(mg－F·sinα)
a＝(F‖－f)/m＝(F·cosα－μmg＋μF·sinα)/m＝(F/m)·(cosα＋μ·sinα)－μg
同理，可得当该力是向下时：
f＝μ·(mg＋F·sinα)
a＝(F/m)·(cosα－μ·sinα)－μg
g取9.8m/s^2
当力向上时，f＝5.79N，a＝5.60m/s^2；
当力向上时，f＝9.89N，a＝4.58m/s^2。

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佩服，英文让我一头雾水

困难大概在翻译上吧。题目倒不难。
水平地面上放着一件4kg的物体，物体和地面之间的动摩擦系数为0.2，有一大小为30N，与水平线夹角20度的力作用在物体上。求摩擦力和物体加速度。
很简单的题，自己算算看吧。有问题我明天来看，实在太困。...

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困难大概在翻译上吧。题目倒不难。
水平地面上放着一件4kg的物体，物体和地面之间的动摩擦系数为0.2，有一大小为30N，与水平线夹角20度的力作用在物体上。求摩擦力和物体加速度。
很简单的题，自己算算看吧。有问题我明天来看，实在太困。

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