Energy - practice problems - page 7 of 11

Number of problems found: 207

Cooker
A current of 2 A passes through the immersion cooker at a voltage of 230 V. What work do the electric field forces do in 2 minutes?
Transformer oil temperature
The transformer is oil-cooled and transforms a power of 20 MW with an efficiency of 92%. Determine the temperature of the oil at the outlet of the transformer if the oil was 20 °C when it entered the transformer. 2.5 liters of oil will flow through the tr
Heating element power
A heating element with a resistance of 1.6 Ω is used to heat the car's rear glass. The body is connected to the battery in the car, which has a voltage of 12 V. a) What is the power input of the heating element? b) How much heat does the heating element g
Copper heat calculation
What heat do we need to supply a copper body weighing 8 kg to raise its temperature by 136 degrees Celsius?
Strawberry harvest calculation
On the farm, twelve part-timers planned to harvest a crop of strawberries in 5 days. On the fifth day in the weather forecast, they reported rain. How many part-timers will they need to harvest the strawberries in four days?
Heat capacity
In a clay vessel there is water with a mass of m = 0.80 kg and a temperature of t₁ = 15°C. An Indian woman took from a fireplace four basalt stones, each with a mass of m₂ = 0.2 kg and with a temperature of t₂ = 450°C, and
A hammer
A hammer weighing 500 g hits the nail at a speed of 3 m/s. What is the average force acting on the nail, which penetrates the board to a depth of 5 cm?
Energy on impact
A stone weighing 200 g falls in a free fall for 3 s. Find its kinetic energy on impact.
Kinetic energy comparison
Compare the kinetic energy of a man weighing 80 kg who runs at a speed of 2 m/s and missiles weighing 20 g fired at 400 m/s.
Aircraft kinetic energy
The 150t aircraft takes off at a speed of 288 km/h and, after a while, reaches a speed of 900 km/h. Determine the change in the kinetic energy of the aircraft.
Kinetic energy
A car traveling at a speed of 25 km/h increased the speed to a) 75 km/h b) 100 km/h when exiting the highway. How many times has its kinetic energy increased?
Hammer fall height
From what height does a hammer weighing 200 kg fall if its initial potential gravity was 6 kJ?
The elevator
The elevator car weighing 400 kg rises from the third to the fifth floor. By what value will the potential gravitational energy of the cabin increase? What useful work will the elevator motor do? The height of one floor is 5 m.
Gravitational potential energy
We lift a weight of 2 kg to a height of 50 cm above the top of the table. Determine its gravitational potential energy: a) relative to the tabletop, b) relative to the floor if the table top is 1 m above the floor.
Positional energy
What velocity in km/h must a body weighing 60 kg have for its kinetic energy to be the same as its positional energy at the height of 50 m?
Kinetic energy calculation
A boy weighing 50 kg moves horizontally by 10 m. What is his kinetic energy at a speed of 1 m/s?
Positioning energy increase
A boy weighing 50 kg moves horizontally by 10 m. How much has his positioning energy increased?
3 phase load
Two wattmeters are connected to measure power in a 3 phase balanced load. Determine the total power and power factor if the two wattmeters read 1000 watts each (1) both positive and (2) the second reading is negative.
Kilowatt-hours
If the Lewis family used 648 kilowatt-hours of electricity in 12 days at the same usage rate, how many kilowatt-hours should they use in 24 days?
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

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