Practice and study guide for the test
▪ Energy transformations-types of energy ▪ Machines- not needed for this test ▪ Motion- not needed for this test
What are the parts of a battery? Anode +, Cathode -, and electrolyte How does a battery work? Chemical reaction allows flow of electrons What energy is in a battery? Potential chemical energy
How is energy stored in a battery? Chemical Potential Energy What energy transformations take place between a battery and a light bulb? Battery and motor? Chemical Potential Energy Kinetic Energy Electric Energy Light/Rotational Energy Heat Energy What are wet cell and dry cell batteries? Wet= liquid electrolyte, Dry= Paste electrolyte
How does charge time affect stored energy in a battery? Longer charge = more stored energy, until chemical reaction is totally reversed and battery will no longer charge Which draws more energy, the light bulb or the motor? The motor draws more because in our tests, it used the battery power quicker than the light bulb with evenly charged batteries.
What is force: A push or a pull What is elastic force? The resistant force exerted that wants to return something to its original state (rubber/elastic) What is gravitational force? The pull of objects toward a larger object (toward the center of the earth) What is frictional force? A force that opposes motion like sliding friction or air friction.
Weight vs. mass? Weight is a measure of gravitational force (we typically use spring scales). Weight changes based on gravitational pull (100N on earth would be 16.7N on the moon). Mass is a measure of the amount of matter in an object (we always use a balance to find mass). Mass does not change (100g=100g). Mass and weight are often the same on earth.
How does surface type affect frictional force? Smoother surfaces typically create less friction. Rougher surfaces typically create more friction between objects. How does weight affect frictional force? More weight was more pressure on the surface and a greater amount of friction was created. Surface area does not have a large impact of frictional force.
Which battery configuration provides the best performance to a motor? Why? Series connections have the most voltage because the voltage of each battery is added to the total. This creates more force from the motor, but if one connection fails, they all do. Parallel connections do not increase voltage so performance is low. However, they are reliable and work even if one cell fails. Hybrid connections can be the best of both.
If energy is the ability to do work, what is work to a scientist? Work happens when a force (Newton) is applied to an object and it moves a measurable distance (meter). W=F x D.
Power is the rate at which work is done. How do scientists calculate power? Scientists use the formula: Power=Work/time Power is known as a Watt, or 1Nm/sec. If it takes 45 Joules and 5 seconds for Mr. Jez to move a box, how many Watts were used? ??? P=W/t P=45/5 = 9Joules/sec., or 9 Watts
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