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Ch 7 Work and Energy Physics for Scientists and Engineers
Ch 7 Work and Energy Physics for Scientists and Engineers 3 ed Giancoli
26
Physics
Undergraduate 1
11/04/2013

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Cards

Term
Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5 min longer. Compare the work against the wall they each do.
Definition
Neither of them do any work.
Term
What does the graphs that illustrates Hooke's Law (the spring force) look like
Definition
[image]
Term

A simple pendulum, consisting of a mass m and a string, swings upward, making an angle θ with the vertical. The work done by the tension force is

[image]

Definition
zero.
Term

[image]

What is the mass of the pendulum 'bob' in the figure?

Definition

1 kg

 

W = mgd

9.8/(9.8*1m) = 1kg

Term

What is the total mechanical energy, ME, of the pendulum?



[image]

Definition

9.8 J

 

ME = PE+KE

ME = 9.8 + 0

Term

What is the maximum kinetic energy of the pendulum?


[image]

Definition

9.8J

 

 

Term
What is the potential energy, PE, at Point B and D?[image]
Definition

4.9J


W=mad

W = 1kg * 9.8 * .5m

Term
At Point B and D what is the relationship between the kinetic energy, KE and[image] the potential energy, PE?
Definition
KE = PE
Term
What is the speed of the pendulum at Point B and D?[image]
Definition

3.1 m/s


KE = (mv^2)/2

mad = (mv^2)/2

2mad=mv^2

2ad=v^2

sqrt(2ad)=v

Term

What is the speed of the pendulum at Point C?


[image]

Definition

4.4 m/s

 

((mv^2)/2) = mad

note= distance traveled is 1m

 

 

Term
A simple pendulum, consisting of a mass m, is attached to the end of a 1.5 m length of string. If the mass is held out horizontally, and then released from rest, its speed at the bottom i[image]s
Definition

5.4 m/s


KE = mv^2/2

sqrt(2ad) = v

Term
A 4-kg mass moving with speed 2 m/s, and a 2-kg mass moving with a speed of 4 m/s, are gliding over a horizontal frictionless surface. Both objects encounter the same horizontal force, which directly opposes their motion, and are brought to rest by it. Which statement best describes their respective stopping distances?
Definition

The 2-kg mass travels twice as far as the 4-kg mass before stopping.

 

Term
A 4-kg mass moving with speed 2 m/s and, an otherwise identical, 2-kg mass moving with a speed of 4 m/s, are gliding over a horizontal surface with friction and are brought to rest by it. Which statement best describes their respective stopping distances?
Definition

he 2-kg mass travels greater than twice as far.



retarding force

Term

A force that Object A exerts on Object B is observed over a 10-second interval, as shown on the graph. How much work did Object A do during that 10 s?


[image]

Definition
25J
Term

A force that Object A exerts on Object B is observed over a 10-second interval, as shown on the graph. What is the average power output of A into B?



[image]

Definition

2.5W

 

Watt = Work/time

Term
The resultant force you exert on a shopping cart, for a 10 s period, is plotted on the graph shown. How much work did you do during this 10 s interval?
[image]
Definition
Zero
Term

The resultant force you exert on a shopping cart, for a 10 s period, is plotted on the graph, shown. What is the average power?


[image]

Definition
The average power is zero.
Term

How much work was required to bring the 1000-kg roller coaster from Point P to rest at Point Q at the top of the 50 m peak?


[image]

Definition

490,000 J


W = mad

1000*9.8*50

Term

If the roller coaster leaves Point Q from rest, how fast is it traveling at Point R?


[image]

Definition

31.3 m/s


KE = mv^2/2

mad = mv^2/2

sqrt(2ad) = v


Term

If the roller coaster leaves Point Q from rest, what is its speed at Point S (at the top of the 25-m peak) compared to its speed at Point R?


[image]

Definition

[image]



Term

What was the total work done on you by all the forces in the universe between the time just before you awoke this morning and right now?


Definition
Zero.
Term
Two cars, starting from rest at the same place, travel by different routes to the same destination. One of the cars passes the other as they drive through it. Which of the following statements will be true?
Definition
The work done by gravity is the same on both.
Term
The work done by friction, f, is equal to
Definition

equals -fd, where d is the total distance moved.


The angle is always 180 degrees.

Term

A 102 kg man climbs a 5.0 meter high stair case at constant speed. How much work does he do?

 

 

Definition
5000 J
Term

A ball is released, from rest, at the left side of the loop-the-loop, at the height shown (h = 2R). If the radius of the loop is R and there is no friction, what vertical height does the ball rise to on the other side?


[image]

Definition
2R
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