What's the power of a man's work on the car

What's the power of a man's work on the car

It depends on the speed of the car, i.e. P = FV

A person pushes a 500N car with 30n force along the horizontal direction at a constant speed on the horizontal ground
A. The resistance of the car is 500nb. The pressure of the car to the ground is 30nc. The supporting force of the ground to the car is 30nd. The supporting force of the ground to the car is 500N

Under the action of downward gravity, upward supporting force, forward thrust and backward friction, the trolley moves at a uniform speed, so the force on the trolley in the horizontal and vertical directions is balanced, so the resistance f = f push = 30n, so a is wrong; the supporting force F = g = 500N, so D is correct, C is wrong; the pressure of the trolley on the ground and the supporting force of the ground on the trolley are force and reaction Force, so the car on the ground pressure is equal to the support force, the size of 500N, so B error; so choose D

Use 20n force to push the car forward at a constant speed on the horizontal road. What is the ground resistance on the car? Why?

20 N! According to the balance of the two forces, the front and rear forces are equal, so that the speed can be uniform!

A classmate pushes a wooden box with a weight of 500N along the horizontal direction to make it move forward at a constant speed on the horizontal ground. If the friction force on the wooden box is 200N, then the human thrust force is 200N______ N. What is the resultant force on the wooden box______ N．

(1) The wooden box is under the action of friction and thrust in the horizontal direction, and the wooden box is in the state of uniform linear motion, so the friction and thrust are a pair of balance forces. According to the condition of two forces balance, the thrust is equal to the friction, which is equal to 200N. (2) the thrust and friction are equal in size, opposite in direction, and on the same line, It can be determined that the resultant force on the wooden box is zero, so the answer is: 200; 0