# Energy - practice problems

#### Number of problems found: 181

- 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 - Conductive 83502

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? - Temperature 83492

How much heat is needed to turn 1kg of ice at a temperature of -10℃ into steam at a temperature of 100℃?

- Calculate 83490

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= 5000kg! - Another 83290

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? - Mechanical 83220

An airplane weighing 100 tons flies at an altitude of 11 km at a speed of 850 km/h. What is its kinetic, potential, and total mechanical energy? - Liters 83211

We have 160 L of water at 67°C; how many liters of cold water at 18°C are needed to cool it to 39°C? - Penetrates 83078

A hammer with a mass of 600 g hits the head of a nail at a speed of 5 m/s. If the nail penetrates 3 cm into the wall, what is the average resistive force of the masonry?

- Overcoming 83076

A battering ram weighing 400 g falls from a height of 3 m. Upon impact, the stake hits a depth of 60 cm. What is the average force overcoming the soil resistance? - Concerning 83022

A man with a mass of 80 kg crosses at a speed of 5 m/s through the car of a train traveling at 15 m/s. Indeed, the kinetic energy of a man: and, concerning the car b, relative to the surface of the earth, if the man is traveling in the direction of travel - Determine 83021

Determine the kinetic energy of a car with a mass of 800 kg if it travels at a speed: a) 10 m/s b) 20 m/s - Horizontal 83020

What work must be done to bring a body of mass of 2 kg lying on a smooth horizontal plane from rest to a speed of 2 m/s? - Weighing 82602

What is the kinetic energy of a stone weighing 1 kg that falls in free fall 5 seconds from the start of its motion? g= 10m/s squared.

- Electrical 82513

How long will it take for a current of 8A in a resistance of 30 ohms to develop thermal energy of 3 MJ if the efficiency of converting electrical energy into heat is 90%? - Lighting-650W 82356

In the office will be connected: computer 800W, kettle 2.5KW, lighting-650W, oven 1.9KW; electric stove 3.3KW; air conditioning 6100W. As the smallest cross-section of the cables, we have to bring them to this room. Recalculate for Copper and Aluminum wir - Calculating 82316

From the formula for calculating thermal energy Q=m*c*t, express t and calculate by how many °C 2kg of water must be heated to increase its energy by 126kJ - Horizontal 82197

A cyclist rides along a horizontal path at a constant speed, overcoming a total resistance force of 20 N. What work does he do on a 5 km track? - Perpendicularly 81951

A body of mass 4g is shot perpendicularly from the ground and lands in 8s. What is its kinetic energy at the beginning of its trajectory, what speed does it take off, and where does the distance from the ground stop? Thank you

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