Physics thermodynamics

Question

1. How much the temperature of glass of water will rise after 2100 J heat. Volume of the glass is 250 cm^3?
2. From what height should 1 l of water fall for its temperature to increase 1 degree celsius. (here potential energy converts into internal energy without any loss)
3. Grinding machine processing 10 kg mass steel detail makes 600 kJ work. 40% of work is used to warm the detail. How much the temperature of the detail increased?
4. How much water can you heat up 50 degrees celsius after burning 100 g gasoline fuel

Sorry for my poor English, I'd really appreciate the explanation.

Answer 1

#1. 250cm³ of water has a mass of 250g, specific heat capacity of water can be taken to be 4.2J/g°C

ΔQ = mcΔT

2100 = 250•4.2•ΔT

2100/(250•4.2) = ΔT

2ºC (same as 2K)

#2

mgh = mcΔT

so h = 4.2•1

so the height should be 4.2m

#3

Total work done is 600000J so 40% = 240000J

ΔQ = mcΔT

ΔT = mc/ΔQ

10•490/240000

0.02°C

#4

Energy content of 100g of gasoline may taken as 4640000J

ΔQ = mcΔT

ΔQ/cΔT = m = 22.09kg

Mateusz G, I hope that helps.

Answer 2

Here you go:

1. How much the temperature of glass of water will rise after 2100 J heat. Volume of the glass is 250 cm^3?
2. You need to know the density of water to proceed with this problem. Density of water is particularly easy to remember, 1 g of water = 1 cm^3, so you have 250 g = 0.25 kg of water. Use the equation: energy/heat = m C ΔT. Here, m = mass of water = 0.25 kg, C = specific heat capacity (look it up in SI units). ΔT is the only unknown in the equation once you plug in the values of remaining quantities.
3. From what height should 1 l of water fall for its temperature to increase 1 degree celsius. (here potential energy converts into internal energy without any loss)
4. Again, a useful fact to keep in mind for this problem is that 1 L of water = 1 kg of water. The gravitational PE is m g h where: m = mass of water, g = acceleration due to gravity in SI units, h = unknown height. This energy is related to the change in temperature given what is said in the problem by: m g h = m C ΔT. ΔT is desired to be 1. m cancels on both sides and then you can compute h, the height from which water must fall.
5. Grinding machine processing 10 kg mass steel detail makes 600 kJ work. 40% of work is used to warm the detail. How much the temperature of the detail increased?
6. 40% of 600 kJ = m C ΔT. Here, m = 10 kg, C = specific heat capacity of steel, look it up in SI units. ΔT is the desired change in temperature.
7. How much water can you heat up 50 degrees celsius after burning 100 g gasoline fuel
8. Find out how much approximate energy comes out by burning 100 g fuel. Then assume no losses and equate it to m C ΔT. ΔT = 50, C = specific heat capacity of water. After plugging in the numbers, you will be able to calculate the unknown m, the mass of water in kg.