Friction Test -...

A box is placed on three different surfaces − a marble floor, a cardboard sheet, and a sand paper. The minimum forces required to simply move the box on the surfaces are F_m, F_c, and F_s respectively.

Pappu is applying a large force in order to push a heavy box lying on the floor. Then, his younger brother, Chintu spreads a little bit of oil on the floor. Now, Pappu feels that it has become relatively easier to move the box.

Friction has advantages as well as disadvantages. Dilip prepares a list of some of the advantageous applications of friction, as shown in the given table.

Application of friction

I Walking

II Writing

III Wearing out of shoes

IV Igniting a matchstick

V Gripping an object

Ram and Shyam are pushing two identical boxes. Ram is pushing box I that is placed on a wheel cart, while Shyam is pushing box II that is placed on the ground. Both Ram and Shyam are trying to maintain a steady motion of the boxes.

Three statements regarding friction.

I Friction is caused by the irregularities of the contact surfaces.

II It is easier to push a moving object than it is when the same object at

rest.

III For a given surface, friction remains the same, whatever be the mass of the object placed on it.

Four similar boxes are labelled I, II, III, and IV. The masses of I and III are equal and the masses of II and IV are equal. The mass of box I is smaller than that of box II. Boxes I and II are placed in a grass field and boxes III and IV are placed on a marble floor.

Brahma rolls down a ball from a certain height along an inclined plane. After reaching the bottom of the inclined plane, the ball rolls some distance horizontally along a surface. Brahma uses four different objects as the horizontal surface at the bottom of the inclined plane. The four objects are frosted glass sheet, cardboard sheet, sand paper, and wrinkle-free towel. In each case, he measures the distance travelled by the ball from the bottom of the inclined plane along the horizontal surface.

Four cubical boxes, made up of the same material, are placed on the ground and are pushed with a constant force. d₁, d₂, d₃, and d₄ are the distances travelled by the boxes. They are related as d₃ > d₂ > d₄ > d₁.

There are three types of friction, namely sliding, static, and rolling. They are respectively denoted as f_sl, f_st, and f_roll.