# Mass + third power - practice problems

#### Number of problems found: 20

- Electric cooker

During which time t does an electric cooker with power input P = 500 W and with efficiency n = 75% heat water with mass m = 2 kg and temperature t1 = 10°C to the boiling point (t2 = 100°C). The specific heat capacity of water is c = 4 180 J. Kg-1. K-1 - Concrete column

The concrete column of the highway bridge has the shape of a block with dimensions of 1m x 0.8m x 25m. It should be lifted by crane to a height of 20m. What is the power of his engine if the lifting takes 2 minutes? - The half life

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 145 grams of a radioactive isotope, how much will be left after 3 half-lives? - Wall thickness

The hollow metal ball has an outside diameter of 40 cm. Determine the wall thickness if the weight is 25 kg and the metal density is 8.45 g/cm³. - Friction coefficient

What is the weight of a car when it moves on a horizontal road at a speed of v = 50 km/h at engine power P = 7 kW? The friction coefficient is 0.07 - Power input

The construction lift lifted a load weighing 300 kg to a height of 12 m with a uniform movement. How long has it taken for the load to be lifted if the efficiency is 75% and the engine has a power input of 5 kW? - Orlík hydroelectric plant

The Orlík hydroelectric power plant, built in 1954-1961, consists of four Kaplan turbines. For each of them, the water with a flow rate of Q = 150 m^{3}/s is supplied with a flow rate of h = 70.5 m at full power. a) What is the total installed pow - A car

A car weighing 1.05 tonnes driving at the maximum allowed speed in the village (50 km/h) hit a solid concrete bulkhead. Calculate height would have to fall on the concrete surface to make the impact intensity the same as in the first case! - No smoke

Tobacco company NO-SMOKE adorned its stand at the cigarette-type trade fair with the cigarette-shaped. The dimensions of which were 20 times the size of a regular cigarette. The regular cigarette contains 0.8 mg of nicotine. How much nicotine would a gian - Density 2

What is the density of a piece of driftwood with a mass of 25 grams and a volume is 30 cm to the 3rd power? And how do I figure it out? - Tower model

Tower height is 300 meters, weight 8000 tons. How high is the model of the tower's weight of 1 kg? (State the result in the centimeters). The model is made from exactly the same material as the original no numbers need to be rounded. A result is a three-d - Granite cube

What is the weight in a kilogram granite cube with an edge of 0.5 m if 1dm³ of granite weight 2600 g? - Hollow sphere

The steel hollow sphere floats on the water plunged into half its volume. Determine the outer radius of the sphere and wall thickness, if you know that the weight of the sphere is 0.5 kg and the density of steel is 7850 kg/m^{3} - BMI index

Calculate BMI (body mass index, an index indicating obesity, overweight, normal weight, underweight) man weighing m = 71 kg and height h = 170 cm. The index is calculated according to equation (formula): BMI = (m)/(h^{2}) With BMI index is possibl - Iron sphere

Iron sphere has weight 100 kg and density ρ = 7600 kg/m³. Calculate the volume, surface, and diameter of the sphere. - Elevator

In homes with more floor elevators are used. For passenger transport, the most commonly used traction elevator counterweight. The top of the shaft engine room with the engine. The car is suspended on a rope, which is guided up over two pulleys to the coun - Cube

The cube weighs 11 kg. How weight is a cube of the same material if its dimensions are 3-times smaller? - Sphere

The surface of the sphere is 12100 cm^{2}, and the weight is 136 kg. What is its density? - Pump

What power has a pump output to move 4853 hl of water to a height of 31 m for 8 hours? - Hollow sphere

Calculate the weight of a hollow stříbrné sphere (density 10.5 g/cm^{3}) if the vnitřní diameter is 15 cm and wall thickness is 1 mm.

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Mass - practice problems. Third power - practice problems.