What is the effect of mass on friction Essay
To conduct this experiment, certain materials will be required. These include the following: 2 force meters (one that measures forces up to 5 Newtons and one that measures forces up to 10 Newtons), a mass i.e. a block of wood of about 15cm3, a table or any smooth surface, a strip of slightly grainy sandpaper and another strip of more grainy sandpaper. The experiment will be set up as shown below (fig 1).Fig 2This experiment was set up into two sections, firstly the effect of mass on dynamic friction and then the effect of mass on static friction.Dynamic Friction: For the dynamic friction experiment, the force of friction will be read off the force meter. This is due to Newton’s second law stating that Fnet = ma. When the block is being pulled along at constant speed, the acceleration is 0 so Fnet = 0. Therefore P = F and so the force shown on the force meter is equal to the frictional force.A hook should first be placed into the block of wood so that it may be pulled along by the force meter. Then the block must be massed and its mass recorded (see table of results) along with its weight (for this experiment 100g = 1N). The mass is then placed onto the first surface and the force meter hooked onto it. Refer to the pilot test to know which force meter would be more suitable at this stage. The block is then pulled along the surface at constant speed and the reading on the force meter should be recorded in the table of results. Repeat this reading two or three times to increase its reliability and then calculate an average of all the readings. Remember to include the repeat readings and the average in your table of results. The experiment should then be set up again using the same block of wood and the same surface but by adding a mass onto the block thus increasing its weight. The new mass and weight of the block should also be recorded in the table of results. The block is then pulled along at constant speed by the force meter and its reading recorded along with the repeat readings. Repeat this about 7 times, each time adding an extra mass on ( the mass being added on should be the same each time).This whole procedure must then be repeated on each surface using the same block of wood, the same surfaces and materials and the same intervals of masses to ensure fair testing. For each experiment there should only be one variable that changes: the mass, all others should be controlled and kept constant.Static Friction: This experiment is set up in the exact same way, keeping the same variables and materials. This time, the block should not be pulled along the surface at constant speed but the force meter should be pulled gently until the block moves. The reading must be taken just as the block moves. This should be repeated as in the dynamic friction experiment and the same masses should be added. All readings should be recorded in a separate table.Now that the experiment is prepared, a pilot test can be carried out. In this pilot test the range of readings will be chosen along with which surfaces to choose from. Our range of masses was chosen to be from 0 – 1 kg with 8 readings on each of the three surfaces. A choice of five surfaces was offered and the three chosen were the ones that differentiated the most from each other. Very grainy sandpaper was supplied but during the pilot test it was found that as it the grains were so large, the lighter masses would just glide right over them.Friction is a force that tries to oppose motion. It is caused when two surfaces are in contact, by the roughness of the materials rubbing against each other, deformations in the materials, and a molecular attraction between materials. If looked through a microscope, friction on the molecular level is due to the unevenness of the surfaces. The two surfaces would have bumps, hills and valleys that would interfere with the sliding motion. If mass was to be added to these surfaces, the bumps and valleys would be pushed harder together, locking them tighter together making it harder to move them. This means that as more masses are added onto the block, the reading on the force meter will go up proportionally. Therefore if we plot a graph of the force on the force meter over the weight, a straight line through the origin should be obtained.