Two equal and opposite forces acting on two objects. When studying acting force and reaction force, it is often aimed at two objects at the same time. It is often wrong to talk about acting force and reaction force without the objects.
Common examples in life
1. Two eggs collide with each other.
Explanation: In daily life, eggs always collide with an edge of a hard object to break them, while senior chefs always beat another egg with one egg. If the breaking strength of the two eggs is the same, the beaten egg is easier to break.
2. Interaction while swimming
Explanation: As we all know, in breaststroke, the feet push the water backwards, and the water is subjected to backward force, so the human body is subjected to forward reaction force, which is the propulsive force obtained by the human body.
3. The reverse thrust of the rocket
Explanation: When the rocket is lifted off, its tail jets downward, and the rocket body and the ejected gas are a pair of interacting objects. When the rocket jets downward, the ejected gas simultaneously produces an upward reaction force on the rocket, which is the driving force for the rocket to rise. This power is not provided by the reaction force of the surrounding air on the rocket.
4. Tap the desktop with your hands
Explanation: We will feel pain when we accidentally hit the desktop. Moreover, the greater the strength of the hand, the more painful it will feel. What caused this? The main reason is that when we beat the desktop, we are also reacted by the desktop. Among them, that hand that strike the table is a force object, and the table is a stress object; The hand feels pain, the table is a force object, and the hand is a force object. These two forces are interactive.
Step 5 row a boat
Explanation: The paddle paddles backwards, and the ship moves forward. The paddle paddles backwards, and the paddle gives water a backward force. Because the forces between objects are mutual, the water also gives the paddle a forward force.
6. Action and reaction of people in the process of walking
Explanation: When we walk, we will find that the speed and difficulty of walking are different on the smooth ground and the rough ground. This is because there are three pairs of interactions in the process of walking. They are the backward friction of people against the ground and the forward friction of the ground against people; The pressure of people on the ground and the supporting force of the ground on people; It is precisely because of these three forces that the gravity of the earth to man and the gravity of man to the earth form the process we are walking.
Summary: There are many examples of action and reaction in life, such as: one object is placed on another, and the two show different actions respectively; Another example is our actions when the ship comes ashore, which also reflects the relationship between action and reaction. The above is only a partial analysis for everyone, and students can continue to observe these phenomena in life, thus generating interest in learning physics.
What are action and reaction?