How to calculate the force when people fall down

1. Hello, this needs to consider the moment of inertia, consider the moment of inertia, use the moment of momentum balance conditions to set up equations, or use simple force system balance conditions

2. Well, first of all, I have to criticize the problems of your school. It's a mess. Yeah, I think so. Take the sole of the foot as the center of the circle, height as the radius, through the fall time can be obtained. Angular velocity, times radius. Get the linear velocity of the head. In weighing the weight of people multiplied by two percent, get the head

3. In fact, the injuries are all the same. The center of gravity should be at the back of the waist, while the back is down. The height of the center of gravity is lower than that of the soles of the feet. Theoretically, the injury will be lighter if the back is down. However, when a person jumps from a high place, the soles of the feet fall down, and he has an instinctive reaction, that is, his legs will bend like springs to relieve the impact force.
in addition, if the height is too high, no matter how he falls down, The injuries are very serious. But if the height of the next two floors is lower, the injury will be lighter with the soles of the feet facing down

4. 1 Generally, the impact of an ordinary punch is 200 pounds
Bruce Lee's punch can reach 600 pounds
because one pound and 0.4545 kg
the impact of an ordinary punch is about 90 kg
(2) an ordinary person can hit four punches in one second
the distance between the punch and the close is almost 0.7 m
then his boxing speed is 5.6 M / s
1 m / S is equal to 3.6 km / h< (3) it takes 10 seconds for an average person to run 50 meters fast
the speed is 5 meters / second
the speed is about 2 meters / second when running normally
equivalent to 7.2 kilometers / hour
so the average running speed is 1 / 3 of the boxing speed
(4) the part of a person's fist is from elbow to palm
the weight of this part is about 1 kg
the weight of a person About 60 kg
a person will proce 90 kg force when he punches at a mass of 1 kg
a person will proce 30 kg force when he punches at a speed of 1 / 3
a person will proce 1800 kg force when he strikes at the same time
which is equivalent to 20 fists hitting you at the same time
(V) if it is a 70 km / h car
then the above number should be multiplied by 10
if the car weighs 1500 kg
then the above number If you multiply it by 25,
that is, when a car collides with a person, it will proce about 450000 kg of force
equivalent to 5000 fists hitting you at the same time
(6) standard men's basketball: 0.6-0.65 kg
standard women's basketball: 0.51-0.55 kg
teenagers' Basketball: 0.47-0.5 kg
children's basketball: 0.3-0.34 kg

5. In this problem, the person who jumps from the moving car originally moves forward at the same speed as the car. When the person jumps from the moving car, his feet will stop under the action of ground friction after landing on the ground, and his upper body will still keep the original motion state e to inertia, so he will fall in the direction of the car, The reasonable order of these four sentences is (4) 1 (2) 3.
so D

6. In the process of walking, the upper body maintains a relatively constant speed

feet in the air: this foot has a forward and downward speed before landing. When landing, the downward speed naturally decreases to 0, but how can the forward speed be offset? You need to rely on the friction between your foot and the ground when you land. When your foot lands, the huge friction between the sole of your foot and the ground immediately reces the forward speed of your foot to 0

feet on the ground: this foot is always under the action of the "push" force squeezed by the leg muscles. It relies on the friction between the ground and the sole of the foot and the horizontal force of the push force to balance, so that your foot is stationary relative to the ground, and other parts of the body move until the other foot falls to the ground

banana peel has two functions, one is to rece the friction when the feet in the air fall to the ground, the other is to rece the friction when the feet on the ground push back. In short, it is to make your life not in the right track. After the foot deviates from the fixed track, your center of gravity deviates, resulting in unbalanced moment of the center of gravity, causing your body to rotate and fall to the ground.

7. The height of each person is 180cm and the mass is mkg
under 1000 times of gravity and 1000 mg of gravity,
suppose that when he falls down (assumed to be forward), he makes an accelerated rotation with his feet as a fixed point. When he stands, his center of gravity is 100 cm above the ground and the contact time with the ground is 0.5 s. from
MGH = MV ^ 2 / 2
ft = MV
we can get that: F is about 30 mg. At that moment, the weight of about 30 people was on him.

8. When a person is standing on the bus, when the car suddenly starts, his feet are affected by the friction of the bottom of the car, which makes the bottom of his feet move with the car. However, his upper body remains in the original static state e to inertia, so he will fall backward.
so the answer is: back; Friction; Inertia

9. Two people fell to the ground under gravity