Energy - practice problems
In mathematics and physics education, energy represents the capacity to do work or cause change, measured in joules. Key forms include kinetic energy (KE = ½mv²), potential energy (PE = mgh), and thermal energy. The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. Mathematical problems involving energy often require understanding quadratic relationships, systems of equations, and calculus for changing rates. Energy calculations appear in mechanics, thermodynamics, electricity, and chemistry. Students learn to apply formulas, convert between energy units, and analyze energy transformations in physical systems.Number of problems found: 197
- An electricity
If the Rodriguez family used 520 kilowatt-hours of electricity in 12 days, how many kilowatt-hours should they use in 6 days at the same usage rate? - Heat energy
Energy is measured using the unit Joule (J). Temperature is measured using the unit degree Celsius °C). To increase the temperature of 1 liter of water by 1°C, 4200 J of heat energy is required. (a) Kelly wants to increase the temperature of 2 liters of w - Electrical 11
An electrical device produces 4.2 MJ of work per hour at an efficiency of 0.53 (53%). What is the power input of this device? - Rotational motion of a cylinder
Calculate the kinetic energy of a cylindrical body of radius r= 0.08 meter and mass m= 1.5kg at time t= 5 s, if this body rotates around an axis passing through the center of the cylinder with a constant acceleration Ԑ= 5 rad/s², if at time t=. - Water + temperature
We supplied 1365 kJ of heat to water weighing 5 kg and initially at 20°C. To what temperature did it heat up? - Heating water
5 kg of water warmed up by 10°C. How much heat did the water absorb? (Remember that 1kg of water needs 4,200J of heat to raise its temperature by 1°C.) - Heating 2
The heating coil of the stove has an electrical resistance of 80 ohms and is connected to an electrical voltage of 230V. Calculate the electrical energy consumed in a year (365 days) if it is switched on for 2 hours a day. How much will we pay for the ene - Spiral - iron
An electric iron is connected to a 230 V voltage source. Its heating coil has an electrical resistance of 100 ohms. Calculate the power of the iron and the electric current flowing through the coil. - Aluminum ignote
At what temperature did the temperature stabilize if an aluminum ignote weighing 45 kg and at a temperature of 15°C received 4.8 MJ of heat? The specific heat capacity of aluminum is 896 J/kg°C. - Capacity of iron
What was the initial temperature of an iron object weighing 30 kg that, when heated to 39 degrees Celsius, absorbed 3.5 kJ of heat? The specific heat capacity of iron is 450 J/kg/°C. - Calorimetric equation
A 200g aluminum cylinder at 180°C was dropped into 3kg water at 25°C. At what temperature did the resulting temperature stabilize? The specific capacity of water is 4200 J/kg °C, aluminum 896 J/kg °C, - Specific heat
How much heat must we add to turn 25 kg of ice at a temperature of -15 degrees Celsius into water with a temperature of 23 degrees? Specific heat of fusion 333 kJ/kg. - By mass
How much heat must we supply to completely convert potassium weighing 45 kg at a temperature of 22.4 °C into potassium at a temperature of 98 °C? The specific heat of fusion is 25.5 kJ/kg, the melting point is 63.32 °C. The specific heat capacity of potas - Elevator efficiency
To what height will an elevator motor with a power of 25 kW and an efficiency of 48.6% transport a cabin weighing 445 kg with seven people (the average weight of one person is 64 kg) if it takes 54 seconds? - Motor efficiency
Calculate the power input of a motor operating at an efficiency of 58% that will lift an elevator car (weighing 390 kg) with twenty boxes (each 25 kg) to a height of 85 m in 29 seconds. - Staircase - escalator
A moving staircase moves downwards at a speed of 0.6 m/s. The staircase makes an angle of 45° with the horizontal. A person weighing 80 kg walks upwards at a speed of 0.9 m/s. Determine the distance covered by the person and the work done by him before he - Soap bubble
A conductive soap bubble with a radius of r=2 cm and charged to a potential of φ= 10000 V will burst into a drop of water with a radius of r1= 0.05 cm. What is the potential φ1 of the drop? - Heat for Phase Change
How much heat is needed to turn 1kg of ice at a temperature of -10℃ into steam at a temperature of 100℃? - Engine power Calculate the engine power of a truck moving at a constant speed of v= 30 km/h on a road with a 5% gradient when the weight of the truck with the load m= 5000 kg!
- Petra chair work
Petra pushed a chair from one room to another with a force of 60N. She did 300 J of work. How far did Petra push the chair?
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