How big is the force? A 50 kilogram object falls down vertically at an altitude of 50 meters. When it falls to the ground, how much force does it have in contact with the ground? Who can figure it out? Just give me an answer! The last time I saw a man jump from a building, I wanted to know how much force he had when he touched the ground? There was no time

How big is the force? A 50 kilogram object falls down vertically at an altitude of 50 meters. When it falls to the ground, how much force does it have in contact with the ground? Who can figure it out? Just give me an answer! The last time I saw a man jump from a building, I wanted to know how much force he had when he touched the ground? There was no time

It is necessary to know the time of interaction with the ground to calculate the average force with momentum theorem. This time is very short and needs to be measured with highly intelligent instruments

When a car runs in a straight line on a horizontal highway, assuming that the resistance it receives is constant, the speed at which the car reaches the rated power and moves at a constant speed is VM
A. The acceleration of a car is directly proportional to the traction it receives when it starts. B. the car starts with constant power, and may do uniform acceleration. C. after the car runs at the maximum speed, if you want to reduce the driving speed, you can reduce the traction power. D. if the car starts with uniform acceleration, the final speed of uniform acceleration can reach VM

A. According to Newton's second law, a = f − FM. Where f = PV, because V increases, f decreases, so a is not proportional to F, so a is wrong; B. start with constant power, speed increases, according to P = FV, traction decreases, according to Newton's second law, acceleration decreases, and makes variable acceleration linear motion. So B is wrong; C. when the car's speed is maximum, traction equals resistance, then B is wrong F = F.P = FVM, reduce the traction power, then p decreases, f remains unchanged, then the speed decreases, so C is correct; D, when the car does uniform acceleration linear motion, when the speed reaches a certain value, the power reaches the rated power, the speed continues to increase, the power remains unchanged, then the traction force decreases, and do variable acceleration linear motion, so the final speed of uniform acceleration can not reach the maximum speed, so D is wrong; so C is selected