How to calculate the falling force
Publish: 2021-04-14 00:34:01
1. http://ci..com/cgAVXfQKm7 "39564;"35777;"9a27
2. What is falling force? If it is on the earth, when an object falls, it is subjected to
gravity: Mg and air resistance f (generally negligible, in fact, it also receives the buoyancy of the air), and the resultant force of the two is the falling force
gravity: Mg and air resistance f (generally negligible, in fact, it also receives the buoyancy of the air), and the resultant force of the two is the falling force
3. It's the experiment of eggs hitting the earth. My classmates and I have done this experiment before, but the eggs didn't break. We used the principle of crushing energy consumption at that time. In fact, there are many good ways to give you a link to see it. http://..com/q?word=%BC%A6%B5%B0%D7%B2%B5%D8%C7%F2&ct=17&pn=0&tn=ikaslist&rn=10
theoretical basis:
1. Expression of momentum theorem: ft = △ P
where △ P refers to the change of momentum, f refers to the size of impulse, and t refers to the action time of force
e to the constant change of momentum △ P ring the falling process of the egg, the force F on the egg is inversely proportional to the acting time t of the force, that is, the greater t is, the smaller f is, and the smaller the force acting on the egg is. In this way, the eggs don't break easily
2. The relationship between air resistance F and air density ρ、 The effective cross-sectional area s is proportional to the square of the falling velocity V, and the resistance can be expressed as F = C ρ SV2, where C is the drag coefficient, generally between 0.2 and 0.5, ρ= 2 kg / m3, the object will fall at a constant speed after a period of time, which is called the ultimate speed
we can find some daily phenomena as follows:
raindrops fall in the air with faster speed and greater air resistance. When the resistance increases to equal to the gravity of the raindrop, the two forces balance and the raindrop begins to fall at a constant speed
parachutists open their parachutes in the air, and with the larger cross-sectional area of the parachute, they can achieve greater air resistance and land more slowly. These are the applications of this formula in life
after understanding this, the acceleration of the device will not be considered as 9.8m/s2
3. All objects have inertia. At the moment when the whole device falls to the ground, the device is still. However, e to inertia, the egg will continue to move, causing extrusion and collision with the device, which is easy to damage
a variety of solutions:
1. Parachute type:
parachute type, as the name suggests, is to use parachute to increase the air resistance, so that the egg and the whole device can land smoothly
this scheme is the easiest to think of, because parachute jumping and spacecraft deceleration all use this method, and the effect is very good. The safety is very high, so that the whole device can fall at a low speed. The weight of the device will not be very heavy. The only drawback is that too much atmospheric disturbance will make the experimental device erratic, poor accuracy, often can not fall to the designated position, thus affecting the competition results
2. Outer packaging type:
outer packaging type is to use more damping materials to wrap the eggs tightly. Such as foam, cotton, various filling materials, etc. Through the buffering effect of these materials, the purpose of protecting eggs can be achieved
this scheme is also easy to think of. I believe you've all seen the way to protect valuables with various filling materials in daily life. This is really an effective way. This scheme has high accuracy because it is little affected by air resistance. As the materials used are of minimal density, the weight of the whole device can be minimized. However, the shortcoming is that the whole device is in free falling state, and the speed when it reaches the ground is relatively high, so it requires high firmness and buffering effect of the device, and the safety is slightly poor
3. Tumbler type:
the tumbler type is to make the whole device like a tumbler, rece the center of gravity as much as possible, so that the device can keep a stable state when it falls, and ensure that one face is always on the ground. Then the protection work only needs to be done well in this aspect, so as to save materials
this scheme fully takes into account that the previous scheme may appear in the air rollover phenomenon, and is formed after improvement. Its reliability is much higher than that of the first scheme, with more material saving and higher accuracy. The fly in the ointment is that in order to ensure that the center of gravity of the device is lowered, it is bound to put a large object at the bottom, which greatly aggravates the whole device and will affect the competition results
4. Polyhedron:
polyhedron is to make the whole device into a polyhedron, fix the egg in the center of the polyhedron with a strong rope, so that the whole egg is suspended. After the device lands, no matter which side is on the ground, the eggs will not land, and the eggs will be intact
this scheme does not need additional materials, only needs to make the polyhedral skeleton and a few wires, so the material consumption is extremely saving, so the weight will be greatly reced. Because the air resistance is small, so the stability is good. But this scheme also has a big disadvantage, that is, the polyhedron is not easy to tie, and the degree of firmness is not high. After landing, the eggs may fall apart, and the eggs will be in danger
5. Double balloon type:
double balloon type is to put the egg in a balloon and fill it with a certain amount of air, then put another balloon outside and fill it with an appropriate amount of air. In this way, an air cushion will be formed between the two layers of balloons, which will protect the eggs from the impact of the ground
the material used in this scheme should be the least among all schemes, and the weight is only the weight of two balloons, which can be almost ignored. But there is a fatal disadvantage of this scheme, that is, one of the two layers of balloons is in close contact, without the protection of air cushion. If it lands on this side, everything will be over. In addition, e to its light weight and the influence of air disturbance, its stability is not very good
6. Propeller type:
propeller type is to place a propeller on the top of the whole device, which is driven or remotely controlled by the flowing air to make the propeller rotate, so as to improve the safety and accuracy. It's very much like the flight principle of a helicopter
this scheme reces the falling speed of the device e to the rotation of the propeller, and has higher safety. If it is remote control, the accuracy will be very high. The problem is how to ensure that the propeller is always up. Once the propeller is not up, the accuracy will be impossible. How to ensure the propeller to rotate smoothly is also a problem
7. Glider:
glider, as the name suggests, is to hang the egg under the glider, the whole device will glide in the air, and finally land smoothly
the accuracy of this scheme is extremely poor, and the landing location is uncertain. If the landing point is not limited, this is undoubtedly a good scheme with high security. Under such competition rules, this method is not advocated
8. Salt water type:
salt water type is to prepare a high-density sodium chloride solution to make the eggs float on it. After landing, the salt water acts as a buffer material to ensure that the eggs will not break
this scheme is novel and unique, with brine as buffer, high safety, little influence by air resistance, and high accuracy. But the device is not easy to control. If the device tumbles in the air and salt water spills out, it will not play a protective role. Therefore, it is necessary to ensure that the center of gravity of the device is stable and as low as possible. The weight of this device can not be ignored. After all, the density of brine is much larger than that of foam.
9. Type of straws:
type of straws: Several straws are tied together to form a group of straws. Several groups of straws are built into a pyramid, and the eggs are clamped in the middle and fixed with adhesive strips. Because the straw is hollow, it can play a buffer role
this scheme has a wide range of materials, light weight and small volume, so it has good accuracy. As for the safety, it may be a little worse. After all, the buffer effect of the straw is limited
10. Integrated:
integrated is the combination of several protection measures, and the devices are also various
there is no doubt that the safety of the integrated device will be greatly improved. It's hard to say whether accuracy has improved or decreased. However, one thing is certain, that is, the total weight of the device is greatly increased, which may affect the competition results< br />… …
theoretical basis:
1. Expression of momentum theorem: ft = △ P
where △ P refers to the change of momentum, f refers to the size of impulse, and t refers to the action time of force
e to the constant change of momentum △ P ring the falling process of the egg, the force F on the egg is inversely proportional to the acting time t of the force, that is, the greater t is, the smaller f is, and the smaller the force acting on the egg is. In this way, the eggs don't break easily
2. The relationship between air resistance F and air density ρ、 The effective cross-sectional area s is proportional to the square of the falling velocity V, and the resistance can be expressed as F = C ρ SV2, where C is the drag coefficient, generally between 0.2 and 0.5, ρ= 2 kg / m3, the object will fall at a constant speed after a period of time, which is called the ultimate speed
we can find some daily phenomena as follows:
raindrops fall in the air with faster speed and greater air resistance. When the resistance increases to equal to the gravity of the raindrop, the two forces balance and the raindrop begins to fall at a constant speed
parachutists open their parachutes in the air, and with the larger cross-sectional area of the parachute, they can achieve greater air resistance and land more slowly. These are the applications of this formula in life
after understanding this, the acceleration of the device will not be considered as 9.8m/s2
3. All objects have inertia. At the moment when the whole device falls to the ground, the device is still. However, e to inertia, the egg will continue to move, causing extrusion and collision with the device, which is easy to damage
a variety of solutions:
1. Parachute type:
parachute type, as the name suggests, is to use parachute to increase the air resistance, so that the egg and the whole device can land smoothly
this scheme is the easiest to think of, because parachute jumping and spacecraft deceleration all use this method, and the effect is very good. The safety is very high, so that the whole device can fall at a low speed. The weight of the device will not be very heavy. The only drawback is that too much atmospheric disturbance will make the experimental device erratic, poor accuracy, often can not fall to the designated position, thus affecting the competition results
2. Outer packaging type:
outer packaging type is to use more damping materials to wrap the eggs tightly. Such as foam, cotton, various filling materials, etc. Through the buffering effect of these materials, the purpose of protecting eggs can be achieved
this scheme is also easy to think of. I believe you've all seen the way to protect valuables with various filling materials in daily life. This is really an effective way. This scheme has high accuracy because it is little affected by air resistance. As the materials used are of minimal density, the weight of the whole device can be minimized. However, the shortcoming is that the whole device is in free falling state, and the speed when it reaches the ground is relatively high, so it requires high firmness and buffering effect of the device, and the safety is slightly poor
3. Tumbler type:
the tumbler type is to make the whole device like a tumbler, rece the center of gravity as much as possible, so that the device can keep a stable state when it falls, and ensure that one face is always on the ground. Then the protection work only needs to be done well in this aspect, so as to save materials
this scheme fully takes into account that the previous scheme may appear in the air rollover phenomenon, and is formed after improvement. Its reliability is much higher than that of the first scheme, with more material saving and higher accuracy. The fly in the ointment is that in order to ensure that the center of gravity of the device is lowered, it is bound to put a large object at the bottom, which greatly aggravates the whole device and will affect the competition results
4. Polyhedron:
polyhedron is to make the whole device into a polyhedron, fix the egg in the center of the polyhedron with a strong rope, so that the whole egg is suspended. After the device lands, no matter which side is on the ground, the eggs will not land, and the eggs will be intact
this scheme does not need additional materials, only needs to make the polyhedral skeleton and a few wires, so the material consumption is extremely saving, so the weight will be greatly reced. Because the air resistance is small, so the stability is good. But this scheme also has a big disadvantage, that is, the polyhedron is not easy to tie, and the degree of firmness is not high. After landing, the eggs may fall apart, and the eggs will be in danger
5. Double balloon type:
double balloon type is to put the egg in a balloon and fill it with a certain amount of air, then put another balloon outside and fill it with an appropriate amount of air. In this way, an air cushion will be formed between the two layers of balloons, which will protect the eggs from the impact of the ground
the material used in this scheme should be the least among all schemes, and the weight is only the weight of two balloons, which can be almost ignored. But there is a fatal disadvantage of this scheme, that is, one of the two layers of balloons is in close contact, without the protection of air cushion. If it lands on this side, everything will be over. In addition, e to its light weight and the influence of air disturbance, its stability is not very good
6. Propeller type:
propeller type is to place a propeller on the top of the whole device, which is driven or remotely controlled by the flowing air to make the propeller rotate, so as to improve the safety and accuracy. It's very much like the flight principle of a helicopter
this scheme reces the falling speed of the device e to the rotation of the propeller, and has higher safety. If it is remote control, the accuracy will be very high. The problem is how to ensure that the propeller is always up. Once the propeller is not up, the accuracy will be impossible. How to ensure the propeller to rotate smoothly is also a problem
7. Glider:
glider, as the name suggests, is to hang the egg under the glider, the whole device will glide in the air, and finally land smoothly
the accuracy of this scheme is extremely poor, and the landing location is uncertain. If the landing point is not limited, this is undoubtedly a good scheme with high security. Under such competition rules, this method is not advocated
8. Salt water type:
salt water type is to prepare a high-density sodium chloride solution to make the eggs float on it. After landing, the salt water acts as a buffer material to ensure that the eggs will not break
this scheme is novel and unique, with brine as buffer, high safety, little influence by air resistance, and high accuracy. But the device is not easy to control. If the device tumbles in the air and salt water spills out, it will not play a protective role. Therefore, it is necessary to ensure that the center of gravity of the device is stable and as low as possible. The weight of this device can not be ignored. After all, the density of brine is much larger than that of foam.
9. Type of straws:
type of straws: Several straws are tied together to form a group of straws. Several groups of straws are built into a pyramid, and the eggs are clamped in the middle and fixed with adhesive strips. Because the straw is hollow, it can play a buffer role
this scheme has a wide range of materials, light weight and small volume, so it has good accuracy. As for the safety, it may be a little worse. After all, the buffer effect of the straw is limited
10. Integrated:
integrated is the combination of several protection measures, and the devices are also various
there is no doubt that the safety of the integrated device will be greatly improved. It's hard to say whether accuracy has improved or decreased. However, one thing is certain, that is, the total weight of the device is greatly increased, which may affect the competition results< br />… …
4. mgh=3×10×9=270
5. Let the velocity v = (2GH) ^ 1 / 2 of an object with mass n fall freely from high h, and the velocity decreases to 0 after time T
the orientation is positive
(f-mg) t = 0 - (- MV)
F = Mg + m (2GH) ^ 1 / 2 / T
impact force F = Mg + m (2GH) ^ 1 / 2 / T
the orientation is positive
(f-mg) t = 0 - (- MV)
F = Mg + m (2GH) ^ 1 / 2 / T
impact force F = Mg + m (2GH) ^ 1 / 2 / T
6. The calculation formula of object falling time: time = root (2 × height ÷ The calculation formula of mass procing force is: gravity = mass × Gravity acceleration
generally 9.8m/s ^ 2
generally 9.8m/s ^ 2
7. When falling from the height of H = 40m, the falling time t, H = GT ^ 2 / 2, so t = 2 √ 2 = 2.83m/s, landing speed V, v = GT = 28.3m/s, the force F is related to the time from landing to rest.
8. It's calculated as follows: impulse I = ft = momentum MV, so the force F = MV / T
generally, the collision time is also related to the speed. It's like a fast car bumping into a person, and the person flies off. If the car is pushed slowly, you will be pushed away for a long time
V = (2GH) ^ 0.5 = (2x10x5) ^ 0.5 = 10 m / s, and the person's thickness will be more than 10 cm, The collision time is almost 0.1 / 10 = 0.01 seconds, f = 1300 * 10 / 0.01 = 13 million n, which is almost the same. Anyway, it must be fried
generally, the collision time is also related to the speed. It's like a fast car bumping into a person, and the person flies off. If the car is pushed slowly, you will be pushed away for a long time
V = (2GH) ^ 0.5 = (2x10x5) ^ 0.5 = 10 m / s, and the person's thickness will be more than 10 cm, The collision time is almost 0.1 / 10 = 0.01 seconds, f = 1300 * 10 / 0.01 = 13 million n, which is almost the same. Anyway, it must be fried
9. It depends on the volume. For example, if a piece of 100 square meters paper weighs 1 kg and hits people, do you think people will die? Of course not!
10. It should know the impact time
50kg object falling 3000m speed is about 245m / S (g = 10m / S2), if the impact time is 0.5 seconds, then use the formula: MV = ft to get f = 24500n.
50kg object falling 3000m speed is about 245m / S (g = 10m / S2), if the impact time is 0.5 seconds, then use the formula: MV = ft to get f = 24500n.
Hot content