Mountain roads are often around the hillside, winding up the mountain, so that the car can get up the mountain Mountain roads often circle the hillside, winding up the mountain, so that the cars can get up the mountain (1) Increase power (2) Improve mechanical efficiency (3) Reduce the required traction (4) Reduce the work required

Mountain roads are often around the hillside, winding up the mountain, so that the car can get up the mountain Mountain roads often circle the hillside, winding up the mountain, so that the cars can get up the mountain (1) Increase power (2) Improve mechanical efficiency (3) Reduce the required traction (4) Reduce the work required

First imagine an extreme: if you lift the car directly to the top of the mountain, the traction force should be greater than or equal to the gravity of the car. Just like an object is placed on an inclined plane, the traction force only needs to be greater than or equal to Mg * sin α. α is the inclination angle between the slope and the horizontal plane sin α ≤ 1, so the traction force is smaller than the original. In other words, the slope and water

A car runs at a constant power and speed on a straight road. In the process of driving, the car increases its traction,
A car runs at a constant speed with constant power on a straight road. In the process of driving, the car increases the traction force. According to the content of physics in grade two (F > F), the speed of the car should be increased. But in the power learning of grade three, P = FV, the speed will decrease when the traction force increases. Isn't that a contradiction?

Now the car is running at a constant power. After increasing the gravity, the power is required to remain unchanged, so the speed must be reduced. For example, when the car is going uphill, the speed is reduced to increase the traction force
When the traction is increased without constant power, as you say, the car is accelerating. At this time, the power of the car will also increase

On the North-South straight road, there are three cars, car a, car B and car C. The people in car a see car B moving southward at a constant speed, the people in car C see car a moving northward at a constant speed, and the people in car B see the trees moving southward at a constant speed. Which of the three cars may be stationary relative to the ground?

Because the people in car B see the trees on the roadside moving southward at a constant speed, car B must move northward relative to the ground; the people in car a see car B moving southward at a constant speed, so car a must move northward relative to the ground at a speed greater than that of car B; the people in car C see car a moving northward at a constant speed, so car C may be stationary

On the North-South straight road, there are three cars, car a, car B and car C. when people in car a see car B moving southward at a constant speed, people in car B see trees moving southward at a constant speed, and people in car C see car a moving northward at a constant speed, then ()
A. Only car a B. only car B. only car C. only car C. only car a and car C

Because the people on car B see the trees on the roadside moving southward at a constant speed, car B must move northward relative to the ground; when the people on car a see car B moving southward at a constant speed, car a must move northward relative to the ground at a speed greater than that of car B; when the people on car C see car a moving northward at a constant speed, car C may be stationary, moving southward or northward The vehicle speed is less than C, so C is selected