问题 计算题

如图所示,小球被轻质细绳系住斜吊着放在静止的光滑斜面上,设小球质量m=0.5kg,斜面倾角α=30°,悬线与竖直方向夹角θ=30°,光滑斜面的质量M为3kg,置于粗糙水平面上,整个装置处于静止状态。

求:(1)悬线对小球拉力大小.

(2)地面对斜面的摩擦力的大小和方向.

答案

(1)2.9N(2)1.4N 方向水平向左

题目分析:(1)以小球为研究对象受力分析可得:

Tsin300=Nsin300

Tcos300+Ncos300=mg

联立解得;T=

(2)对小球和斜面的整体而言,f=Tsin300=,方向水平向左。

阅读理解
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The 小题1:________ to keep fit
Eating properly
You should have proper breakfast because it can 小题2:________ you with necessary energy.
You should have enough for lunch and little for 小题3:________.
Sweet snacks and desserts are tasty, 小题4:________ you shouldn't eat too much.
Keeping off germs
It's necessary for you to 小题5:________ your teeth every day, cough or sneeze into your arms’ and wash your hands often to stop germs from 小题6:________.
小题7:________ regularly
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Staying connected
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