静摩擦系数公式
摩擦力是一种阻止两个物体相互运动的力。当两个物体接触时,它们会产生摩擦力,这是一种接触力。
Friction is defined as the opposition offered by the surfaces that are in contact when they were in relative motion.
根据物体的类型,摩擦有不同的种类,可以抵抗滑动物体的运动,也可以抵抗两个物体在彼此相对运动时的运动。摩擦的类型如下,
- 静摩擦力
- 滑动摩擦
- 滚动摩擦
- 动摩擦
- 流体摩擦。
静摩擦力
静摩擦顾名思义,静态意味着静止,因此当物体处于静止位置时,静摩擦会作用于物体。当两个物体都静止或其中一个物体稍微倾斜或倾斜时,反对物体运动的摩擦力称为静摩擦力。
静摩擦系数公式
静摩擦系数可以用以下公式计算:-
μs = F /N
Where
F = Static force of friction
μs = coefficient of static friction
N = Normal force
静摩擦示例
- 汽车停在斜坡上,车轮与路面的静摩擦力使汽车保持在原位。
- 鼻子上的眼镜是静摩擦的另一个常见例子。
- 戴手表、把衬衫挂在衣架上、戴戒指、系裤子的腰带都是生活中常见的静摩擦例子。
- 窗玻璃上的水滴。
- 由于水泥的某些强力作用而粘在屋顶上的瓷砖,这里的摩擦原因是化学物质。
静摩擦定律
- 在静摩擦中,最大力与接触面积无关。
- 法向力与静摩擦的最大力相比,这意味着,如果法向力增加,物体在不移动的情况下所能拥有的最大外力也会增加。
示例问题
问题 1: 一个 400 N 的力施加在仍然在地板上的 10 kg 的盒子上。如果摩擦系数为 0.3,静摩擦的值是多少?
解决方案:
Given,
Force F = 400 N,
Coefficient of friction, μs = 0.3
Static friction is given by Fs = μs Fn
= 0.3 × 400 N
Fs = 120 N.
问题 2:陈述静摩擦定律。
回答:
- In static friction, the maximum force is independent on the area of contact.
- The normal force is comparative to the maximum force of static friction it means that, if the normal force increases, the maximum external force that the object can posses without moving, also increases.
问题 3:放在地板上的盒子承受 90N 的力,静摩擦系数为 0.4。求摩擦力。
解决方案:
Given,
Force applied or normal force N = 90 N
Coefficient of friction = 0.4
Static friction can be calculated as: F = μs × N.
F = 0.4 × 90
= 36 N
问题 4:一个 40Kg 的箱子放在地板上,水平承受 60N 的力,静摩擦系数为 0.2。求摩擦力。盒子会从它的位置移动吗?
解决方案:
Given,
Force applied = 60 N
Coefficient of friction = 0.2
Normal force Fn = mg = 40 × 10 = 400 N.
Static friction can be calculated as: F = μs × N.
F = 0.2 × 400
= 80 N
We can see that static frictional force i.e. 80N, is greater than applied force 60 N which means that box will remain in its position.
问题 5:在静摩擦系数为 0.2 的箱子上施加 50 N 的力。求摩擦力。
解决方案:
Given,
Force applied or normal force N = 50 N
Coefficient of friction = 0.2
Static friction can be calculated as: F = μs × N.
F = 0.2 × 50
= 10 N
问题6:在静摩擦系数为0.3 的静摩擦系数为20Kg 的箱子上水平施加30N 的力。求摩擦力。确定遗嘱箱是否移动?
解决方案:
Given,
Force applied = 150 N
Coefficient of friction = 0.3
Normal force Fn = mg = 30 × 10 = 300 N.
Static friction can be calculated as: F = μs × N.
F = 0.3 × 300
= 90 N
We can see that static frictional force i.e. 90N, is greater than applied force 30 N which means that box will not move from its position.
问题 7:将一个质量为 20 公斤的盒子放在光滑的表面上。这两个表面之间的静摩擦力为 30 N。求静摩擦系数?
解决方案:
Given,
Mass of box, m = 20 kg
Friction between them, F = 30 N
Coefficient of static friction μs = ?
We know that,
Normal force, N = mg
So, N = 20 × 9.81 = 196.2 N (g = 9.81)
For coefficient of static friction is,
μs = F/N
μs = 30/196.2
μs = 0.153