Question

5. Collect at least six objects of different materials. Check them for their friction
by sliding an object on their surfaces. Now arrange them according to their friction
(high to low). How their friction can be reduced? Suggest some methods according
to the materials
(6 marks)​

Answer 1

Experimental Procedure:

Create a ramp. Sand the wood block and board so that the surfaces are smooth and will not cause splinters. Using a ruler or a yard stick measure 8" from each end of the board. Prop one end of the board up on a stack of books.

Place the block of wood at the top of the ramp. Release the block of wood, do not push it. The wood should slide down the board. If it does not slide increase the incline of the ramp by stacking more books.

Using a stop watch record the time it takes for the block of wood to slide from the top mark to the bottom mark. As soon as the front end of the block crosses the top mark start your timer. Once the back end of the block crosses the end mark stop your timer. Repeat 2 more times.

Record your times on a chart and calculate the average time between the 3 trials.

Cover the surface of the board with aluminum foil. Use tape to secure the foil. Repeat steps 3 & 4.

Cover the surface of the board with a piece of cotton cloth. Repeat steps 3 & 4.

Coat the surface of the board with a this layer of oil (cooking oil, mineral oil). Repeat steps 3 & 4.

Choose 3 more materials to test on the surface of the board. Use your background research for ideas on what kinds of materials to test. Repeat steps 3 & 4.

From your chart compare the average times for each surface. Which had the fastest time? Which had the slowest time?

Calculate speed for each trial using the average time: length (inches) from start to end mark / average time.

Reducing Friction

There are several ways to reduce friction:

The use of bearing surfaces that are themselves sacrificial, such as low shear materials, of which lead/copper journal bearings are an example.

Replace sliding friction with rolling element friction, such as with the use of rolling element bearings.

Improve overall lubrication either by changing viscosity, using differing or improved additives or through the use of different lubricants themselves, i.e., synthetics, solids, etc.

hope it will help you........

Answer 2

Answer:

The answer is as follows

Explanation:

Six objects :

1. Wooden block
2. Copper balls
3. Lead balls
4. iron block
5. ice cubes
6. aluminum block

The various methods used to reduce friction are:

• Objects that move in liquid, such as boats, planes, and cars, have a streamlined body shape and reduced liquid to reduce friction between the objects' bodies.
• By polishing the surface, the surface becomes smoother and friction can be reduced.
• Lubricants such as oils and greases can be used to reduce friction between surfaces.
• When rolling an object on a surface, ball bearings can be used to reduce friction between the rolled object and the surface.

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