31) Explain that friction is both a friend and a foe"
वर्णन कीजिए घर्षण किस प्रकार शत्रु और मित्र दोनों हैं।
32) Draw a labelled diagram of the human eye.
मानव नेत्र का नामांकित रेखाचित्र बनाइए।
33) What are sex harmones. Why they are named so? State their function.
लिंग हार्मोन व्या है? उनका नामकरण इस प्रकार क्यों किया गया है। उनके कार्य भी बताइए
34) Define asexual reproduction. Describe two methods of a sexual reproduction in
animals.
अलगिक जनन की परिभाषा लिखिए जंतुओं में अलगिक जनन की दो विधियों का वर्णन कीजिए
35) Classify the material given below as good conductor or poor conductor,
(1) Lemon Juice (ii) Vinegar (iii) Tap water (iv) Vegetable oil (v) Milk
निम्न पदार्थों को सुचालक अथवा हीन बालक के रूप में वर्गीकृत करो
() नींबू का रस (ii) सिरका (iii) टोटी का पानी (iv) वनस्पति तेल (V) दूध
36) During 2020 a pandemic breakout in the world in which millions of people died,
Pandemic has shaken the economy of the world. It started from China but spread out in
the whole world afterwards sharply in America, Russia, India, Britain like countries
These were maximum number of casualties which are still continued. During this
period it is found that people following personal hygiene remained safe It is viral disease
which affects lungs and becomes dangerous for life. You are well aware of this
disease because government is making people aware through newspapers, TV like
communication mediums and people suffering from the disease are placed in Quarantin
domir dirnurend in aboue necesne
Answers
Imagine trying to push a couch across the floor. You push on it with a small force, but it does not move. This is because it is not accelerating. Newton's laws tell you that the net force on the couch must be zero. There must be a second horizontal force acting on the couch, one that opposes your force and is equal in size. This force is static friction force, which is the force exerted on the surface by another when there is no motion between the two surfaces.
Static friction force acts in response to a force trying to cause a stationary object to start moving. If there is no such force acting on an object, the static friction force is zero. If there is a force trying to cause motion, the static friction force will increase up to a maximum value before it is overcome and motion starts.
Now let's look at the formula for static friction force. The static friction force (F(f, static)) is less than or equal to the product of the coefficient of static friction (µ(s)) and the normal force (F(N)).
static friction formula
- The maximum static friction force relates to the normal force in a similar way as the kinetic friction force. In the equation for maximum static friction force, µ(s) is the coefficient of static friction between two surfaces. The maximum static friction force that must be overcome before motion can begin is µ(e depend? The materials that the surfaces are made of play a role. For example, imagine trying to play basketball while wearing socks instead of athletic shoes. You would slip and slide all over the basketball court. Shoes help provide the forces necessary to quickly change directions while running up and down the court. There is more reaction between your shoes and concrete than there is between your socks and a polished wood floor.
This table shows coefficients of static friction (µ(s)) and coefficients of kinetic friction (µ(k)) between various surfaces. The coefficients of friction show how easily one object can slide against another. These coefficients are estimates for each combination of surfaces. Exact measurements of coefficients of friction are quite sensitive to the c