The time 
it takes for the key to fall 44 m is
(notice I'm taking the downward direction to be positive)
The boat, moving at a presumably constant speed, then has 3.0 s to travel 19 m to the point of impact, which means its speed must be
Answer:
Neglecting any frictional losses, the average power delivered by the car's engine is 10565 W
Explanation:
The energy conservation law indicates that the energy must be the same at the bottom of the hill and at the top of the hill.
The energy at the bottom is only the Kinect energy (K_1) of the car in motion, but in the top, the energy is the sum of its Kinect energy (K_2), potential energy (P) and the work (W) done by the engine.
then, the work done by the engine is:
The formulas for the Kinetic and potential energy are:
where, m is the mass of the car, V the velocity, g the gravity and h is the elevation of the hill.
Using the formulas:
Replacing the values:
The negative of this value indicates the direction of the work done, but for the problem, you only care about the magnitude, so the power is W=1690400 J. Now, the power is equal to work/time so you need to find the time the car took to get to the top of the hill.
The average speed of the car is (27+14)/2=20m/s, and t=d/v so the time is:
the power delivered by the car's engine was:
Back emf is 85.9 V.
<u>Explanation:</u>
Given-
Resistance, R = 3.75Ω
Current, I = 9.1 A
Supply Voltage, V = 120 V
Back emf = ?
Assumption - There is no effects of inductance.
A motor will have a back emf that opposes the supply voltage, as the motor speeds up the back emf increases and has the effect that the difference between the supply voltage and the back emf is what causes the current to flow through the armature resistance.
So if 9.1 A flows through the resistance of 3.75Ω then by Ohms law,
The voltage across the resistance would be
v = I x R
= 9.1 x 3.75
= 34.125 volts
We know,
supply voltage = back emf + voltage across the resistance
By plugging in the values,
120 V = back emf + 34.125 V
Back emf = 120 - 34.125
= 85.9 Volts
Therefore, back emf is 85.9 V.
Define the following:
Potential energy: In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
Kinetic energy: In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes.
Mechanical energy:
Chemical energy: chemical energy, Energy stored in the bonds of chemical compounds. Chemical energy may be released during a chemical reaction, often in the form of heat; such reactions are called exothermic. Reactions that require an input of heat to proceed may store some of that energy as chemical energy in newly formed bonds
Sound energy: In physics, sound energy is a form of energy that can be heard by living things. Only those waves that have a frequency of 16 Hz to 20 kHz are audible to humans. However, this range is an average and will slightly change from individual to individual.
Light energy: Light energy is a kind of kinetic energy with the ability to make types of light visible to human eyes. Light is defined as a form of electromagnetic radiation emitted by hot objects like lasers, bulbs, and the sun. Light contains photons which are minute packets of energy.
Nuclear energy: Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by nuclear fission of uranium and plutonium in nuclear power plants
From Greek meaning not divisible.
