　　Friction phenomenon is universal in the life and production process. Sliding friction, rolling friction and static friction will all occur. What factors are their sizes related to? What method can be used to determine their sizes?

　　When two interacting objects move relative to each other or have a tendency to move, they will hinder relative sliding along the tangent direction of the contact surface. This phenomenon is called friction; this kind of force that hinders relative sliding is called sliding friction force. The magnitude of sliding friction is related to the surface roughness of the objects in contact with each other and the positive pressure of the objects, and has nothing to do with the contact area.

　　Purpose

　　1. Learn how to measure friction

　　2. Study the factors affecting the sliding friction

　　experiment equipment

　　Force sensor, friction force experiment teaching aid, cable, USB cable

　　Experimental results

　　Synthesis and Decomposition of Experiment Two

　　Purpose

　　Analyze the decomposition of the force generated by the gravity of the block with the change of the pull angle

　　Experimental principle

　　A vertically placed object is at rest under the balance of gravity and tensile force. The tensile force is formed by the combined force generated by the component forces of two angles. The relationship between the resultant force and the component force can be explored by changing the angle of the two component forces.

　　experiment equipment

　　Computer, force synthesis and decomposition experiment instrument, USB cable

　　Experimental setup

　　Experiment 3 Newton's second law-the relationship between force and acceleration

　　Purpose

　　Study the relationship between tension and acceleration

　　experiment equipment

　　Computer, displacement sensor, USB cable, rail trolley and accessories (trolley + displacement + connecting rod = 203g, the mass of the small tube without cover is 5g).

　　Experimental setup

　　Experiment 4 Conservation of Mechanical Energy (Swing Ball Method Double Photoelectric Gate)

　　Purpose

　　By measuring the value of the kinetic energy and gravitational potential energy of the pendulum ball at any time (position) in the swing process, the change law of mechanical energy is studied.

　　Experimental principle

　　Under the condition that only gravity or elastic force does work on the object (or not under the action of other external forces), the kinetic energy and potential energy (including gravitational potential energy and elastic potential energy) of the object are transformed into each other, but the total amount of mechanical energy remains unchanged. This law is called the law of conservation of mechanical energy. In this experiment, the pendulum ball is only subject to gravity during its fall, so the mechanical energy is conserved.

　　experiment equipment

　　Computer, mechanical energy conservation demonstration instrument, photoelectric gate sensor, two USB cables.

　　experimental device

　　Experiment 5 Capacitor charging and discharging and calculating capacitance

　　Purpose

　　(1) Understand that capacitors can store charges, and they can also release stored charges to form currents;

　　(2) Understand the changes in current and voltage across the capacitor during the charging and discharging process;

　　(3) Understand that the charging and discharging time is related to the power supply voltage, resistance and capacitor size;

　　Experimental principle

　　(1) The parallel plate capacitor is composed of two mutually insulated and very close metal plates. The two poles are respectively connected to the positive and negative electrodes of the power supply, which can make the internal discharge called and the discharge current will continue for a period of time. There is an equal amount of different kinds of charges on the board. This process is called charging. The charging current will continue for a period of time until the voltage between the two plates is equal to the voltage across the power supply, and charging stops. The two poles of the charged capacitor are connected with a wire, the two poles are neutralized, and the capacitor is no longer charged. This process is called discharge.

　　(2) The resistance is added to the circuit to extend the charging and discharging time and facilitate the observation of current and voltage changes;

　　experiment equipment

　　1 voltage sensor, 1 current sensor, 2 USB cables, 6V battery pack, connecting wire, 50Ω or 100Ω sliding rheostat, 2200μF electrolytic capacitor, single pole double throw switch.

　　Experimental results

　　Experiment 6 Mechanical Energy-Thermal Energy Conversion

　　Purpose

　　Understand the transformation of work and energy.

　　Experimental principle

　　When two objects are rubbed together, the work done by overcoming the friction is converted into the internal energy of the object, which increases the temperature.

　　experiment equipment

　　Temperature sensor, computer, copper tube, rubber plug, cotton rope, clamp, flexible foam plastic, etc.