Experiments to measure the magnitude of friction, experimental methods to measure sliding friction

It does not mean that the principle of doing this experiment is "two-force equilibrium".

The condition of the equilibrium of the two forces: the two forces are equal in magnitude; in opposite directions; on the same straight line; Acting on the same object. "Pull the spring dynamometer diagonally upwards with a spring dynamometer" It is obvious that friction and tension are not in the same straight line, so friction is not equal to tensile force, which is the indication of the spring dynamometer.

It should be that the pulling force is greater than the frictional force.

The correct operation method in the experimental process is to pull the spring dynamometer horizontally, when the wooden block moves in a uniform linear velocity, the two forces are balanced, and the indication of the spring dynamometer is equal to the friction force.

The question should indicate that the block did not leave the board. Then the friction force should be equal to the indication of the spring dynamometer; Why, I think you should have learned the most basic coordinate method, decomposing the force into the force on the x and y axes, in this case, the upward tension of the spring can be divided into vertical and horizontal forces. It should be considered that the vertical upward pulling force is perpendicular to the direction of motion of the object, that is to say, this is not done during the whole movement.

Only the force in the horizontal direction does the work. Because the object moves in a uniform linear motion and is in equilibrium, the tensile force of the spring is equal to the frictional force received by the object in the horizontal direction, and the direction is opposite, that is, whether the indication of the spring dynamometer is equal to the friction force.

(1) The factors affecting the sliding friction are: the roughness of the contact surface and the pressure between the objects

2) When measuring sliding friction, it is necessary to pay attention to: let the wooden board move in a straight line at a uniform speed, the wooden board is in a balanced state, and the sliding friction is equal to the tensile force of the spring dynamometer; If the plank does not move in a straight line at a uniform velocity, the sliding friction is not equal to the tensile force of the spring dynamometer

3) From the experimental data in the table, it can be seen that in the two experiments, the contact surface is the same, the greater the pressure, the greater the sliding friction of the wooden board, it can be seen that in the case of a certain contact surface, the greater the pressure, the greater the friction

From the experimental data in the table, it can be seen that in the two experiments, the pressure of the wooden board is the same, and the rougher the contact surface, the greater the sliding friction, so it can be seen that under the condition of a certain pressure, the rougher the contact surface, the greater the friction

Therefore, the answers are: (1) control variable method; (2) Let the plank move in a straight line at a uniform speed;

3) In the case of a certain contact surface, the greater the pressure, the greater the friction; At a certain pressure, the rougher the contact surface, the greater the friction

Experiment 08 Measure the sliding friction of a horizontally moving object.

Prepare a flat concrete floor, a manometer, a friction disc, and a weight. Place the friction disc on the concrete floor, and then place the weight on the friction disc to adjust the pressure value of the manometer to stabilize it in a certain position. The pressure value of the manometer is recorded, and then the friction disc is moved some distance to record the amount of force required.

Hello, glad to answer for you! Friction is the resistance of two objects when they come into contact with each other, and can be measured by the following experiments: prepare a flat concrete floor, a pressure gauge, a friction plate, and a weight.

Place the friction disc on the concrete floor, and then place the weight on the friction disc to adjust the pressure value of the manometer to stabilize it in a certain position. The pressure value of the manometer is recorded, and then the friction disc is moved a distance to record the amount of force required to make the void.

The magnitude of the friction force is calculated based on the recorded data. The magnitude of the frictional force can be calculated by the following formula: f = n, where f is the friction force, is the coefficient of friction, and n is the gravitational force of the object in relative contact with the ground.

The coefficient of friction is the ratio of the frictional force to the gravitational force acting between the objects in contact. The coefficient of friction depends on the material and surface roughness of the object in contact. For example, the coefficient of friction between leather and cement is usually greater than that of plastic and concrete.

In addition, it is important to note that the direction of the frictional force is opposite to the gravitational force of the object in which the friction disc is in relative contact. For example, if the friction disc is sliding upwards, the direction of the frictional force should be downward. Through the above experiments, the magnitude of the frictional force can be measured, and the magnitude of the friction force can be changed by changing the coefficient of friction or the gravitational force acting on the contact object.

The friction coefficient is usually determined by the friction angle method: one of the two objects is tilted as an inclined plane, and the other object slides down along the inclined cavity surface, and the inclination angle is gradually reduced to the object above can slide down at a uniform speed, and then according to the formula: mgsin 0= mgcos 0, get:

Brief introduction. The coefficient of friction is the ratio of the frictional force between two surfaces to the perpendicular force acting on one of their surfaces. It is related to the roughness of the surface, not the size of the contact area.

According to the nature of the motion, it can be divided into dynamic friction coefficient and static friction coefficient. Sliding friction is caused by two objects touching each other and sliding relative to each other.

Balance friction: appropriately raise the right end of the remaining bark plank, and the vertical line difference makes the component of the trolley's gravity along the inclined plane just balance the resistance of the trolley and the paper tape. When balancing the friction, do not tie the string hanging the small disc to the trolley, that is, do not add any traction to the trolley, and let the trolley move at a uniform speed by pulling the dotted paper tape.

Experimental principle: control variable method: firstly, the mass m of the trolley is controlled, and the relationship between acceleration a and force f is discussed; In controlling the mass of the disc and the weight to be constant, that is, the force f is constant, change the mass of the trolley m, and discuss the relationship between acceleration a and m.

Ways to increase beneficial friction:

1) Increase the roughness of the contact surface;

2) increase the pressure;

3) Turning rolling friction into sliding friction;

Ways to reduce harmful friction:

1) Replace sliding friction with rolling friction;

2) Separate the contact surface [form a layer of air cushion or magnetic levitation on the contact surface of the object];

3) reduce pressure;

4) Reduce the roughness of the contact surface of the object.

Summary. 1.Adjustment testing machine:

The measured object is placed on the testing machine and the sliding load is implemented using the inertial mass to measure the sliding friction. 2.Powder testing machine is used: the measured object and powder are mixed in a certain flow ratio, placed on top of the concave test, and then the simulated friction force is applied to measure the sliding friction force; 3.

The wear testing machine is adopted: the measured object and other objects are placed in two vertical planes, and the relative movement between the two objects is controlled by a variable speed motor, so as to measure the sliding friction force; 4.Rolling friction testing machine:

The sliding friction force is measured by placing the two ends of the measured object on the column, then adding opposing rollers, fixing it firmly, and applying gravity to make it slide.

Here are a few things you can try.

1.Adjustment testing machine: the measured object is placed on the testing machine, and the sliding load is implemented with inertial mass to measure the sliding friction; 2.

Powder testing machine is used: the measured object and powder are mixed with a certain flow ratio, placed on top of the concave test, and then the simulated friction force is applied to measure the sliding friction force; 3.Wear testing machine:

The measured object and other objects are placed in two vertical planes, and the relative or only movement between the two objects is controlled by a variable speed motor, so as to measure the sliding friction force; 4.Rolling friction testing machine is adopted: the two ends of the measured object are placed on the column, and then the opposite roller is added, which is fixed firmly, and the gravity of the bush trace is applied to make it slide, so as to measure the sliding friction force.

1. Spring dynamometer.

Prepare a long potato plank with a smooth side and a rough cloth on the other, two cuboids, and a spring dynamometer.

The different sides of a piece of wood are in contact with the surface of the long wooden board, and the wooden block is slowly pulled at a uniform speed to stabilize the spring dynamometer test number, and the spring dynamometer test number is observed and recorded; On the board, the front ruler is superimposed on another plank again, and the above operation is repeated, and the test number of the spring dynamometer is observed.

<>2. Use the weight of constant gravity to drag the object to be measured, make a uniform acceleration linear motion, and measure the acceleration with a dot timer, which can be solved to obtain the friction force.

1. Use the spring dynamometer to drag the object to be measured for uniform linear motion, and the value displayed on the dynamometer is the friction force. 2. The weight of constant gravity is dragged to be measured by the falling, and the linear motion is uniformly accelerated, and the acceleration is measured with a dot timer, and the friction can be solved.

If the static friction is measured, and it is the static friction of the object placed on the horizontal table, then the spring dynamometer can be accurately measured, as long as the dynamometer is pulled horizontally, the object remains still, the number of the dynamometer is how big, how big the friction is!

If the sliding friction is measured, and the object is placed on a horizontal tabletop as an example, the sliding friction between B and A can be accurately measured by pulling the object A below by using the method shown in the diagram.

It is solved by the balance of two forces

The determining factors of the sliding friction are: 1. The amount of pressure 2. The roughness of the contact surface.

Sliding friction: When two objects in contact with each other are in direct contact, squeezing each other, and the contact surface is rough, when the two move relatively, a force that hinders this relative motion will be generated on the contact surface called sliding friction.

Experimental principle: two-force balance.

Experimental equipment: square blocks, towels, wooden boards, glass plates, weights, spring dynamometers.

Experimental steps: 1. When studying the relationship between sliding friction and pressure, place the square object on the wooden board to ensure that the roughness of the contact surface remains unchanged, change the pressure by changing the number of weights on the square block, and make a uniform motion under the pull of the spring dynamometer, and read the spring dynamometer reading. It is concluded that the greater the roughness of the contact surface, the greater the pressure, the greater the sliding friction.

2. When studying the relationship between sliding friction and the roughness of the contact surface, because the roughness is an unmeasurable quantity, the square block is placed on the surface of the towel, the glass surface and the wooden board surface by the conversion method, and the block moves at a uniform speed under the tension of the spring dynamometer, and the spring dynamometer reading is read. It is concluded that the rougher the contact surface and the greater the sliding friction for the same pressure.

3. Conclusion: When the roughness of the contact surface is constant, the greater the pressure, the greater the sliding friction; When the pressure is constant, the rougher the contact surface, the greater the sliding friction.

Chapter 7 Motion and ForceSection 6 "What is the magnitude of friction related to the student's experiment".