Physics
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True or False: Work is a form of energy.
TRUE - Work is a form of energy, and in fact it has units of energy.
True or False: A Watt is the standard metric unit of work.
FALSE - Watt is the standard metric unit of power; Joule is the standard metric unit of energy.
True or False: Units of work would be equivalent to a Newton times a meter.
TRUE - A N*m is equal to a Joule.
True or False: A kg*m2/s2 would be a unit of work.
TRUE - A kg*m2/s2 is a mass unit times a speed squared unit, making it a kinetic energy unit and equivalent to a Joule.
True or False: Work is a time-based quantity; it is dependent upon how fast a force displaces an object.
FALSE - Work is not dependent on how rapidly the force displaces an object; power is time-based and calculated by force multiplied by speed.
True or False: Superman applies a force on a truck to prevent it from moving down a hill. This is an example of work being done.
FALSE - Since Superman does not cause a displacement, no work is done; he is merely holding the car to prevent its descent down the hill.
True or False: An upward force is applied to a bucket as it is carried 20 m across the yard. This is an example of work being done.
FALSE - The upward force does not cause the horizontal displacement so this is a NON-example of work.
True or False: A force is applied by a chain to a roller coaster car to carry it up the hill of the first drop of the Shockwave ride. This is an example of work being done.
TRUE - There is a component of force in the direction of displacement and so this is an example of work.
True or False: The force of friction acts upon a softball player as she makes a headfirst dive into third base. This is an example of work being done.
TRUE - There is a force and a displacement; the force acts in the opposite direction as the displacement and so this force does negative work.
True or False: An eraser is tied to a string; a person holds the string and applies a tension force as the eraser is moved in a circle at constant speed. This is an example of work being done.
FALSE - For uniform circular motion, the force acts perpendicular to the direction of the motion and so the force never does any work upon the object.
True or False: A force acts upon an object to push the object along a surface at constant speed. By itself, this force must NOT be doing any work upon the object.
FALSE - This is clearly work - a force is causing an object to be displaced.
True or False: A force acts upon an object at a 90-degree angle to the direction that it is moving. This force is doing negative work upon the object.
FALSE - If a force acts at a 90-degree angle to the direction of motion, then the force does not do any work at all. Negative work is done when there is a component of force opposite the direction of motion.
True or False: An individual force does NOT do positive work upon an object if the object is moving at constant speed.
FALSE - There are many instances in which an individual force does positive work and yet the object maintains a constant speed. Consider a force applied to lift an object at constant speed. The force does positive work. Consider a car moving at constant speed along a level surface. The force of the road on the tires does positive work while air resistance does and equal amount of negative work.
True or False: An object is moving to the right. A force acts leftward upon it. This force is doing negative work.
TRUE - A force which acts in a direction opposite the motion of an object will do negative work.
True or False: A non-conservative force is doing work on an object; it is the only force doing work. Therefore, the object will either gain or lose mechanical energy.
TRUE - When non-conservative forces do work upon an object, the object will either gain or lose mechanical energy. Mechanical energy is conserved (neither gained nor lost) only when conservative forces do work upon objects.
True or False: Power is a time-based quantity.
TRUE - Power is a rate quantity and thus time-based.
True or False: Power refers to how fast work is done upon an object.
TRUE - This is the definition of power.
True or False: Powerful people or powerful machines are simply people or machines which always do a lot of work.
FALSE - This is not always the case. A machine can do a lot of work but if it fails to do it rapidly, then it is not necessarily powerful. In fact two machines can do the same task (and therefore the same work), yet they can have drastically different power ratings.
True or False: A force is exerted on an object to move it at a constant speed. The power delivered by this force is the magnitude of the force multiplied by the speed of the object.
TRUE - An equation for computing work in constant speed situations is P=F*v.
True or False: The standard metric unit of power is the Watt.
TRUE - Watt is the unit of power? Yes!!
True or False: If person A and person B do the same job but person B does it faster, then person A does more work but person B has more power.
FALSE - Vice versa. If two people do the same job, then they’re doing the same amount of work. The person who does it fastest generates more power.
True or False: The Newton*meter is a unit of power.
FALSE - A N*m is a Joule and that is a unit of work (not power). Think force (N) times distance (m); that’s work (J).
True or False: A 60-kg boy runs up a 2.0 meter staircase in 1.5 seconds. His power is approximately 80 Watt.
FALSE - The work would be (mg)d or approximately 1200 J. The power is work divided by time - 1200 J/1.5 s = 800 W.
True or False: A 300-Newton force is applied to a skier to drag her up a ski hill at a constant speed of 1.5 m/s. The power delivered by the toe rope is 450 Watts.
TRUE - Since force and speed are given, use Power = F*v. The calculation yields 450 W.