Question

Ученикам 7 класса (!!!) вопрос(дядям и тетям старше 13 лет просьба не напрягаться)Ножки стола имеют форму квадрата со стороной 10 см, крышка стола – форму квадрата со стороной 80 см. Давление стола, стоящего на четырех ножках, равно 5 кПа. Каким станет давление стола на пол при переворачивании его на крышку?

Answer 1

Формула давления тела на поверхность: P=F/S, P - давление, F - сила тяжести, S - площадь поверхности, давящая на пол.
Р1 - давление ножек, Р2 - давление крышки, S1 - площадь всех ножек, S2 - площадь крышки.
P1=5000 Па, S1=4*0.1*0.1=0.04 м2, S2=0.8*0.8=0.64м2
F=P1*S1=P2*S2
F=5000*0.04=200Н,
P2=200/0,64=312,5 Па
Ответ: 312,5 Па

Answer 2

Calculation of Pressure on the Table

To calculate the pressure on the table, we need to use the formula:

Pressure = Force / Area

In this case, the force is the weight of the table, and the area is the contact area between the table and the floor.

The weight of the table can be calculated by multiplying the mass of the table by the acceleration due to gravity. However, we are not given the mass of the table, so we cannot calculate the exact weight.

However, we are given the pressure on the table, which is 5 kPa (kilopascals). This means that the force exerted by the table on the floor is equal to the pressure multiplied by the area of contact.

The area of contact between the table and the floor is equal to the area of the four legs of the table. Since the legs are in the shape of a square with a side length of 10 cm, the area of each leg is 10 cm * 10 cm = 100 cm^2.

Therefore, the total area of contact between the table and the floor is 4 * 100 cm^2 = 400 cm^2.

Now, we can calculate the force exerted by the table on the floor:

Force = Pressure * Area

Force = 5 kPa * 400 cm^2

Note: We need to convert the area from cm^2 to m^2 to match the unit of pressure (kPa).

Force = 5 kPa * (400 cm^2 / 10,000 cm^2/m^2)

Force = 5 kPa * 0.04 m^2

Force = 0.2 kN

Therefore, the force exerted by the table on the floor is 0.2 kN (kilonewtons).

Pressure on the Floor when the Table is Flipped

When the table is flipped onto its cover, the force exerted by the table on the floor remains the same. However, the area of contact between the table and the floor changes.

The area of contact between the table and the floor when the table is flipped is equal to the area of the table cover, which is a square with a side length of 80 cm.

Therefore, the area of contact between the table and the floor when the table is flipped is 80 cm * 80 cm = 6400 cm^2.

Now, we can calculate the pressure on the floor when the table is flipped:

Pressure = Force / Area

Pressure = 0.2 kN / (6400 cm^2 / 10,000 cm^2/m^2)

Pressure = 0.2 kN / 0.064 m^2

Pressure = 3.125 kPa

Therefore, the pressure on the floor when the table is flipped onto its cover is approximately 3.125 kPa.

Please note that the calculations provided are based on the given information and assumptions made.