Question

4. Бетонная плита объёмом 2 м3 погружена в воду. Какую силу необхо- димо приложить, чтобы удержать ее в воде; в воздухе?​

Answer 1

Ответ:

Объяснение:

1) В воздухе

$F = m * g = \rho * V * g = 2300 * 2 * 10 = 46 000$ Н = 46 кН

2) В воде

$F = F_G - F_A = m * g - \rho_{H_2O} * g * V = 46000 - 1000 * 10 * 2 = 26000$ Н = 26 кН

Answer 2

#### Calculating the Force Required to Hold the Concrete Slab in Water To calculate the force required to hold the concrete slab in water, we need to consider the buoyant force acting on the slab. The buoyant force is equal to the weight of the water displaced by the slab. The weight of the water displaced can be calculated using the formula: **Weight of water displaced = density of water x volume of water displaced** The density of water is approximately 1000 kg/m^3. Given that the volume of the concrete slab is 2 m^3, we can calculate the weight of the water displaced: **Weight of water displaced = 1000 kg/m^3 x 2 m^3 = 2000 kg** Therefore, the force required to hold the concrete slab in water is equal to the weight of the water displaced, which is 2000 kg. #### Calculating the Force Required to Hold the Concrete Slab in Air To calculate the force required to hold the concrete slab in air, we need to consider the weight of the slab itself. The weight of the slab can be calculated using the formula: **Weight of slab = density of concrete x volume of slab x acceleration due to gravity** The density of concrete is typically around 2400 kg/m^3, and the acceleration due to gravity is approximately 9.8 m/s^2. Given that the volume of the concrete slab is 2 m^3, we can calculate the weight of the slab: **Weight of slab = 2400 kg/m^3 x 2 m^3 x 9.8 m/s^2 = 47040 N** Therefore, the force required to hold the concrete slab in air is equal to the weight of the slab, which is 47040 N. Please note that these calculations assume that the concrete slab is fully submerged in water and that the air is at standard atmospheric conditions.