PE & KE Simple Calc
How much energy does a 4 kg apple have that is thrown at a speed of 2 m/s?
8 J
What energy transformation for an electric blanket?
electrical -> thermal
Energy in motion is known as ...
kinetic energy
Name the 3 ways that heat can be transferred.
conduction, convection, radiation
How much heat is neededto warm 0.098 kg of goldfrom 15°C to 30°C if goldhas a specific heat of 136J/kg°C?
200 J
How much energy does a bird have that weighs 9 N and is sitting on a branch 3 m high?
27 J
What energy transformation for a windmill?
kinetic -> electrical
Energy stored to be used for work done is known as ...
potential energy
This type of energy transfer is through direct contact.
Energy is transferred from a region of __________ kinetic energy to a region of __________ kinetic energy.
Conduction.
higher; lower
What is the height a toy plane can reach that has a mass of 4 kg and is flying at a rate of 9 m/s straight upward? Assume all energy is conserved.
4.13 m
How much energy does a car have when driving 50 km/h with a mass of 700 kg?
67515 J
What energy transformation for fireworks?
chemical -> radiant / sound / thermal
Thermal energy is an example of __________. Explain.
Kinetic energy, because it is the movement of atoms and particles.
______________ is the transfer of thermal energy by the movement of heated fluids from one place to another
convection
A 50 kg gorilla is sitting on the limb of a tree 7 meters above the ground. Use the conservation of energy, what is the height above the ground when they were travelling down at 5 m/s?
5.72 m
What is the mass of a picture that falls off a shelf 6 m high and has 150 J of energy?
2.55 kg
An apple falling off a tree
gravitational potential energy -> kinetic
List the type of energy each object below has (identify whether they're KE or PE).
1. Sandwich
2. Trampoline
1. chemical potential energy
2. elastic potential energy
______________ is the transfer of energy by waves travelling outward in all directions from a source.
radiation (electromagnetic)
A 0.5 kg sample of methanol (c = 2531) at 20.00oC is mixed with a 0.5 kg sample of water (c = 4184) at 95.00oC. Assume no heat loss to the surroundings. What is the final temperature of the mixture?
58.99oC
2531 (Tf -20) = 4184 (95 - Tf)
Solve for Tf = 66.37 oC
What is the speed of a bike with a mass of 10 kg and energy of 250 J?
7.07 m/s
A man eating dinner, then tap dancing.
chemical -> kinetic -> sound/thermal
In a race, two cars have the same mass but different velocities. The car with the slower velocity has ________ kinetic energy than the other car does.
less
As the energy transfers from one substance to the other, the colder substance will ____________ and the warmer substance will __________. This transfer of energy continues until there is no longer a difference in temperature between the two substances, which means we've reached ________.
gain kinetic energy (temp increase)
lose kinetic energy (temp decrease)
thermal equilibrium
A 0.500 kg cube of iron (450 J/kg°C) is cooled from 100°C to 10°C, by dunking into water. Water (4180 J/kg°C) rises from 0°C to 10°C. What mass of water is needed?
Tf - Ti = 100-10 = 90°C (for iron)
Q iron = (0.5)(90)(450) = 20,250 J
Q lost by iron = Q gained by water = 20,250 J
20,250 J = m (4140)(10) = 0.48 kg