Energy - practice problems - page 3 of 11

Number of problems found: 207

KiloJoules energy
In the washing machine, 6 liters of water were heated from a temperature of 22 degrees to 62 degrees. Find out the weight of 6 liters of water. What heat (in kJ= kiloJoules) did the water receive?
Cooker electrical work
A cooker connected to a 40 V voltage source draws a current of 0.5 A. Determine the amount of electrical work the cooker does in 3 minutes.
Body mass work
What was the body's mass when it moved along a path of 70 dm and did 1.4 kJ of work?
Motor efficiency power
The electric motor has an efficiency of 80% (power and input ratio). What is the power input of this motor if its power is 5 horsepower (HP)? Enter the result in kilowatts (kW) and round to one decimal place (1 HP = 3/4 kW).
Coefficient of friction
A car moves along a horizontal road at a speed of 15 m/s. After turning off the engine, the car traveled a distance of 225 m. What was the coefficient of friction for this motion?
Refreshing drink
For the participants of a meeting a refreshing drink had to be prepared. The mineral water however had in summer the temperature of the room, i.e. 30 °C, for drinking water with a temperature of 10 °C would be suitable. Therefore the secretary took ice fr
Current in the bulb
The bulb is rated 6 V, 0.2 A. Determine the current rating of the bulb.
Cooker heat generation
An immersion cooker has a resistance of 30 ohms and is connected to a voltage of 120 V. How much heat is generated in 2 hours?
Resistor voltage power
Determine the largest voltage on a resistor with a resistance of 150 ohms if the largest permitted electrical power current in the resistor is 2 W.
Calculate energy
A cheetah weighing 38 kg moves at a speed of 108 km/h. Calculate its kinetic energy.
Factory light savings
The factory hall is lit by 76 light bulbs, each of which has an input of 200 W. Determine how much electrical work will be saved annually if the light is on an average of 100 minutes less per day. Consider 260 business days.
Mechanical energy
A stone with a mass of 2 kg falls in free fall from a tower with a height of 80 m. What is its kinetic energy, and what is its potential energy: a) At the beginning of the fall, b) In 1 s from the beginning of the fall, c) Upon impact, d) What is its mech
Tractor friction work
A tractor pulls a tree trunk weighing 1.5 t for a distance of 2 km along a horizontal road at a constant speed. What mechanical work does it do if the coefficient of sliding friction is 0.6?
A box 5
A cereal box states that a 3/4-cup serving contains 90 calories. How many Calories are in 4 cups of cereal?
Kinetic energy
A 100 kg car has a velocity of 15 m/s. What is the car's kinetic energy?
Energy drink
You have 1/5 of an energy drink left. If you drink 1/5 of that, how much of your energy drink did you have left?
A car 6
A car holds 15 liters of fuel. The car consumes 3 liters of fuel each 100 km. We started a trip of 350 km with a full tank of fuel. How much fuel remains in the tank at the end of the trip?
Gas price increase
The smaller bakery had a long-term contract and purchased one MWh of gas for 36 euros in 2021. After the contract expired, it had to switch to the current spot price and pay up to 196 euros for one MWh. By what percentage did the price of electricity for
ZSE year 2022 comparison
Calculate the limit value of monthly electricity consumption in kWh of rates D1 and D2, at which it is worth it to change the rate (from D1 to D2 or vice versa). The energy company offers the following pricelists (very confusing for an ordinary user, espe
What power 2
What power has a pump output to move 4853 hl of water to a height of 31 m for 8 hours? Comparing the power generated by the pump vs. the power generated by the motor, which is more efficient? Which pump or motor generates more pollution if, for every watt

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