Which of the following statements is true of group tasks?

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Work and also Energy Review

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Part A: Forced Choice Questions

1. Which of the adhering to statements are true around work? Include all that apply.

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Work is a kind of energy.A Watt is the conventional metric unit of work-related.Units of work-related would certainly be identical to a Newton times a meter.A kg•m2/s2 would be a unit of work-related.Work is a time-based quantity; it is dependent upon exactly how fast a pressure dislocations a things.Superguy uses a force on a truck to prevent it from relocating dvery own a hill. This is an instance of job-related being done.An upward pressure is applied to a bucket as it is lugged 20 m throughout the yard. This is an example of work being done.A pressure is applied by a chain to a roller coaster auto to bring it up the hill of the first drop of the Shockwave ride. This is an instance of occupational being done.The force of friction acts upon a softround player as she makes a headinitially dive right into 3rd base. This is an example of work being done.An eraser is tied to a string; a perchild holds the string and also applies a stress pressure as the eraser is moved in a circle at continuous rate. This is an instance of job-related being done.A pressure acts upon an object to press the object along a surface at consistent rate. By itself, this pressure should NOT be doing any kind of job-related upon the object.A force acts upon an item at a 90-degree angle to the direction that it is relocating. This force is doing negative job-related upon the object.An individual pressure does NOT carry out positive job-related upon an item if the object is moving at continuous speed.An object is moving to the appropriate. A force acts leftward upon it. This force is doing negative job-related.A non-conservative pressure is doing work-related on an object; it is the just force doing work. Because of this, the object will certainly either gain or shed mechanical energy.


a. TRUE - Work is a form of energy, and also in fact it has devices of power.

b. FALSE - Watt is the typical metric unit of power; Joule is the typical metric unit of energy.

c. TRUE - A N•m is equal to a Joule.

d. TRUE - A kg•m2/s2 is a mass unit times a speed squared unit, making it a kinetic power unit and identical to a Joule.

e. FALSE - Work is not dependent on how rapidly the pressure displaces an object; power is time-based and also calculated by force multiplied by rate.

f. FALSE - Due to the fact that Supermale does not reason a displacement, no job-related is done; he is merely holding the vehicle to proccasion its descent dvery own the hill.

g. FALSE - The upward pressure does not reason the horizontal displacement so this is a NON-instance of work.

h. TRUE - There is a component of pressure in the direction of displacement and so this is an example of occupational.

i. TRUE - Tbelow is a force and a displacement; the force acts in the oppowebsite direction as the displacement and also so this pressure does negative job-related.

j. FALSE - For uniform circular activity, the force acts perpendicular to the direction of the movement and so the force never does any occupational upon the object.

k. FALSE - This is clearly work-related - a pressure is bring about an item to be disinserted.

l. FALSE - If a force acts at a 90-level angle to the direction of activity, then the pressure does not perform any job-related at all. Negative occupational is done when tbelow is a component of pressure oppowebsite the direction of movement.

m. FALSE - There are many kind of instances in which an individual pressure does positive work-related and yet the object maintains a continuous speed. Consider a force used to lift an object at continuous speed. The pressure does positive job-related. Consider a automobile moving at consistent speed alengthy a level surconfront. The pressure of the road on the tires does positive work while air resistance does and equal amount of negative job-related.

n. TRUE - A force which acts in a direction opposite the activity of an item will carry out negative work-related.

o. TRUE - When non-conservative forces execute work-related upon an item, the object will certainly either get or shed mechanical power. Mechanical power is conserved (neither got nor lost) only as soon as conservative forces perform work-related upon objects.

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Definition and also Mathematics of Work
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2. Which of the following statements are true around power? Include all that use.

Power is a time-based amount.Power describes exactly how quick work is done upon a things.Powerful people or effective equipments are ssuggest human being or machines which always perform most work-related.A force is exerted on an object to move it at a constant speed. The power ceded by this pressure is the magnitude of the force multiplied by the speed of the object.The standard metric unit of power is the Watt.If perboy A and perchild B perform the same task yet perchild B does it faster, then perboy A does more occupational yet perchild B has actually even more power.The Newton•meter is a unit of power.A 60-kg boy runs up a 2.0 meter stairsituation in 1.5 seconds. His power is about 80 Watt.A 300-Newton force is used to a skier to drag her up a ski hill at a constant speed of 1.5 m/s. The power ceded by the toe rope is 450 Watts.

Answer: ABDEI

a. TRUE - Power is a price quantity and for this reason time-based.

b. TRUE - This is the meaning of power.

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c. FALSE - This is not constantly the situation. A machine have the right to carry out many occupational however if it falls short to carry out it promptly, then it is not necessarily effective. In fact 2 machines have the right to execute the very same job (and also therefore the same work), yet they can have substantially various power ratings.

d. TRUE - An equation for computer job-related in constant rate instances is P=F•v.

e. TRUE - Watt is the unit of power? Yes!!

f. FALSE - Vice versa. If 2 civilization carry out the exact same job, then they're doing the very same amount of job-related. The perboy who does it fastest generates even more power.

g. FALSE - A N•m is a Joule and that is a unit of work (not power). Think force (N) times distance (m); that's job-related (J).

h. FALSE - The occupational would certainly be (m•g)•d or about 1200 J. The power is work separated by time - 1200 J/1.5 s = 800 W.

i. TRUE - Due to the fact that pressure and also rate are provided, use Power = F•v. The calculation yields 450 W.

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3. Consider the complying with physical instances. For each case, identify the angle between the shown force (in boldface type) and also the displacement ("theta" in the work-related equation).

a. 0 degreesb. 180 degreesc. 90 degreesd. 30 degreese. 60 degrees
A rightward used force is provided to dislocation a television set to the best. - Answer: A - 0 degreesThe force of friction acts upon a rightward-relocating auto to carry it to a sheight. - Answer: B - 180 degreesA waiter uses an used force to balance the weight of a tray of plates as he carries the tray throughout the room. - Answer: C - 90 degreesThe pressure of air resistance acts upon a vertically-falling skydiver. - Answer: B - 180 degreesThe pressure of friction acts upon a basesphere player as he slides right into third base. - Answer: B - 180 degreesAn used force is provided by a freshmale to lift a World Civilization book to the peak shelf of his locker. - Answer: A - 0 degreesA bucket of water is tied to a string and also tension offers the centripetal pressure to save it moving in a circle at continuous rate. - Answer: C - 90 degreesAn applied force acting at 30-degrees to the horizontal is supplied to disarea an item to the ideal. - Answer: D - 30 degreesA team of footround players use an used force to press a sled across the grass. - Answer: A - 0 degreesThe tension in the elevator cable causes the elevator to increase at a continuous rate. - Answer: A - 0 degreesIn a physics lab, an applied force is exerted parallel to a airplane inclined at 30-degrees in order to disarea a cart up the incline. - Answer: A - 0 degreesAn applied force is exerted upwards and also rightwards at an angle of 30-levels to the vertical in order to dislocation a things to the right. - Answer: E - 60 degreesA child rests on the seat of a swing which is supported by the tension in its cables; he swings from the highest possible position to its lowest position. - Answer: C - 90 degrees

Answer: See questions above; explanations given below.

a. The forward motion is do to the forward pushing; if the force and also motion are in the very same direction, then the angle is 0 degrees.

b. Friction opposes motion and also as such does negative work; the angle is 180 degrees.

c. The pressure is vertical and the displacement if horizontal; they make a 90 level angle.

d. Air resistance opposes activity and also as such does negative work; the angle is 180 levels.

e. Friction opposes activity and as such does negative work; the angle is 180 levels.

f. The frosh applies an upward force to cause an upward displacement; the angle is 0 degrees.

g. For unidevelop circular activity, the pressure is inwards and the displacement at each instant is tangent to the circle; these two vectors make a 90 degree angle.

h. This is a straightforward question; no tricks here.

i. The forward motion is do to the forward pushing; if the pressure and also activity are in the exact same direction, then the angle is 0 levels.

j. The cable pulls up on the elevator and also the elevator is disput upward; if the force and also activity are in the very same direction, then the angle is 0 levels.

k. The 30-level angle is the incline angle, not necessarily the angle between F and d. The pressure is parallel to the incline and also the cart is disput along the direction of the incline; so the 2 vectors are in the exact same direction and the angle between them is 0 levels.

l. Compare the wording of this to part h. This one is tricky because the angle between F and also d is 60-levels. If you missed it, rereview the question, paying mindful attention to the "with the vertical" component.

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m. As the boy swings, she traces out a circular arc and also as such the stress and anxiety (centripetal) is perpendicular to the direction of motion (tangent).