Though most tennis players generally strive to strike the ball on the

Question

New Project RC Butler 2019  -  Practice 2 RC Passages Everyday   
Passage # 308, Date : 03-Sep-2019
 This post is a part of New Project RC Butler 2019 .  Click here for Details

Though most tennis players generally strive to strike the ball on the racket's vibration node, more commonly known as the "sweet spot," many players are unaware of the existence of a second, lesser-known location on the racket face, the center of percussion, that will also greatly diminish the strain on a player's arm when the ball is struck.

In order to understand the physics of this second sweet spot, it is helpful to consider what would happen to a tennis racket in the moments after impact with the ball if the player's hand were to vanish at the moment of impact. The impact of the ball would cause the racket to bounce backwards, experiencing a translational motion away from the ball. The tendency of this motion would be to jerk all parts of the racket, including the end of its handle, backward, or away from the ball. Unless the ball happened to hit the racket precisely at the racket's center of mass, the racket would additionally experience a rotational motion around its center of mass-much as  a penny that has been struck near its edge  will start to spin. Whenever the ball hits the racket face, the effect of this rotational motion will be to jerk the end of the handle forward, towards the ball. Depending on where the ball strikes the racket face, one or the other of these motions will predominate.

However, there is one point of impact, known as the center of percussion, which causes neither motion to predominate; if a ball were to strike this point, the impact would not impart any motion to the end of the handle. The reason for this lack of motion is that the force on the upper part of the hand would be equal and opposite to the force on the lower part of the hand, resulting in no net force on the tennis players' hand or forearm. The center of percussion constitutes a second sweet spot because a tennis player's wrist typically is placed next to the end of the racket's handle. When the player strikes the ball at the center of percussion, her wrist is jerked neither forward nor backward, and she experiences a relatively smooth, comfortable tennis stroke.

The manner in which a tennis player can detect the center of percussion on a given tennis racket follows from the nature of this second sweet spot. The center of percussion can be located via simple trial and error by holding the end of a tennis racket between your finger and thumb and throwing a ball onto the strings. If the handle jumps out of your hand, then the ball has missed the center of percussion.   1 
 E 
 1. What is the primary message the author is trying to convey?

(A) a proposal for an improvement to the design of tennis rackets
(B) an examination of the differences between the two types of sweet spot
(C) a definition of the translational and rotational forces acting on a tennis racket
(D) a description of the ideal area in which to strike every ball
(E) an explanation of a lesser-known area on a tennis racket that dampens unwanted vibration

2 
 A 
 2. According to the passage, all of the following are true of the forces acting upon a tennis racket striking a ball EXCEPT

(A) The only way to eliminate the jolt that accompanies most strokes is to hit the ball on the center of percussion.
(B) The impact of the ball striking the racket can strain a tennis player's arm.
(C) There are at least two different forces acting upon the racket.
(D) The end of the handle of the racket will jerk forward after striking the ball unless the hall strikes the racket's center of mass.
(E) The racket will rebound after it strikes the ball.

3 
 B 
 3. What is the primary function served by paragraph two in the context of the entire passage?

(A) to establish the main idea of the passage
(B) to provide an explanation of the mechanics of the phenomenon discussed in the passage
(C) to introduce a counterargument that elucidates the main idea of the passage
(D) to provide an example of the primary subject described in the passage
(E) to explain why the main idea of the passage would be useful for tennis players

4 
 D 
4. The author mentions " a penny that has been struck near its edge " in order to

(A) show how the center of mass causes the racket to spin
(B) argue that a penny spins in the exact way that a tennis racket spins
(C) explain how translational motion works
(D) provide an illustration of a concept
(E) demonstrate that pennies and tennis rackets do not spin in the same way

5 
 C 
 5. Which of the following can be inferred from the passage?

(A) If a player holds the tennis racket anywhere other than the end of the handle, the player will experience a jolting sensation.
(B) The primary sweet spot is more effective at damping vibration than the secondary sweet spot.
(C) Striking a tennis ball at a spot other than the center of percussion can result in a jarring feeling.
(D) Striking a tennis ball repeatedly at spots other than a sweet spot leads to "tennis elbow."
(E) If a player lets go of the racket at the moment of impact, the simultaneous forward and backward impetus causes the racket to drop straight to the ground.

chris988226 · Accepted Answer

Can someone explain why correct answer to the last question is C ?
5. Which of the following can be inferred from the passage?
(C) Striking a tennis ball at a spot other than the center of percussion can result in a jarring feeling.

We are told in the first paragraph that there are TWO sweet spots. Moreover, answer to the second question (two sweet spots) contradicts the answer C to the above question. Maybe I am missing something, but it is really incomprehensible to me so far.

BrainLab · Answer

Got this one right 1.E 2.A 3.B 4.D 5.C

The main point is stated in the 1st paragraph: many players are unaware of the existence of a second, lesser-known location on the racket face, the center of percussion,
that will also greatly diminish the strain...

1. What is the primary message the author is trying to convey?  --> General Question (find the main point) 
(A) a proposal for an improvement to the design of tennis rackets  --> You won't find any information about design in the whole passage.... 
(B) an examination of the differences between the two types of sweet spot  --> There are no differences expained in the passage. In the first paragraph 2 Sweet points are stated. Only 2nd point is described in the followinf paragraphs. 
(C) a definition of the translational and rotational forces acting on a tennis racket  --> That's not the main point (see explanation above) 
(D) a description of the ideal area in which to strike every ball  --> It's not the only sweet point, so we can't say that the 2nd sweet point must be used to strike each ball 
(E) an explanation of a lesser-known area on a tennis racket that dampens unwanted vibration  --> CORRECT. Rephrasing of the main point ; All other choices were already eliminated.

2.According to the passage, all of the following are true of the forces acting upon a tennis
racket striking a ball EXCEPT
(A) The only way to eliminate the jolt that accompanies most strokes is to hit the ball
on the center of percussion  --> CORRECT. 2nd sweet point is only one of two possible ways to achieve the elimination of the jolt .
(B) The impact of the ball striking the racket can strain a tennis players arm  --> can be found in paragraph 
(C) There are  at least  two different forces acting upon the racket.  --> can be found in paragraph 
(D) The end of the handle of the racket will jerk forward after striking the ball unless  --> can be found in paragraph
the ball strikes the rackets center of mass. 
(E) The racket will rebound after it strikes the ball  --> can be found in paragraph (bounce back...)
 
This one most diff. for me... B or D ? Picked B at the end....
3.What is the primary function served by paragraph two in the context of the entire passage? 
(A) to establish the main idea of the passage  --> Main idea is stated in the 1st paragraph 
(B) to provide an explanation of the mechanics of the phenomenon discussed in the
passage  -> CORRECT. The 2nd paragraph starts with the words "In order to understand the physics of
this second sweet spot ..." 
(C) to introduce a counterargument that elucidates the main idea of the passage  --> It explains how the 2nd spot works 
(D) to provide an example of the primary subject described in the passage  --> To be honest, I can not eliminate this one, B sounds better for me.... 
(E) to explain why the main idea of the passage would be useful for tennis players  --> it describes the mechanics... tennis player is not mentioned in the paragraph at all !

4.The author mentions “a penny that has been struck near its edge” in order to
(A) show how the center of mass causes the racket to spin  --> The ball causes the racket to spin and not a center of mass 
(B) argue that a penny spins in the exact way that a tennis racket spins  --> can not be found in the paragpraph 
(C) explain how translational motion works  --> rotational motion NOT translational 
(D) provide an illustration of a concept  --> CORRECT. It's used just as illustration.... 
(E) demonstrate that pennies and tennis rackets do not spin in the same way  --> spins like a penny.... ooposite....

5. Which of the following can be inferred from the passage?
(A) If a player holds the tennis racket anywhere other than the end of the handle, the
player will experience a jolting sensation.  -->can not be found in the paragpraph .. to extreme.. 
(B) The primary sweet spot is more effective at damping vibration than the secondary
sweet spot  --> no comparison can be found 
(C) Striking a tennis ball at a spot other than the center of percussion  can  result in a
jarring feeling  --> CORRECT. ...strain on a player's arm. 
(D) Striking a tennis ball repeatedly at spots other than a sweet spot leads to “ tennis
elbow .”  --> can not be found in the paragpraph 
(E) If a player lets go of the racket at the moment of impact, the simultaneous forward
and backward impetus causes the racket to  drop  straight to the ground  --> can not be found in the paragpraph

chris139 · Answer

I'm having mixed feelings about question no. 2.

Specifically, I'm seeing counterarguments for OA (answer A) and arguments for answer C.

A. The only way to eliminate the jolt that accompanies most strokes is to hit the ball on the centre of percussion.

The presented explanations refers to the very beginning of the passage where the author states  "...many players are unaware of the existence of the second, lesser-known location on the racket face, the centre of percussion, that will also greatly diminish the strain on the player's arm..."

Thus, supposedly, centre of percussion together with "sweet spot" constitute two spots. However, those two spots only  "greatly diminish the strain"  and do not eliminate it (as the answer would suggest).

Later on in the passage (end of paragraph 3), however, the author says that  "when the player strikes the ball at the centre of percussion, her wrist is jerked neither forward nor backward"  which suggests that this one place actually "eliminates the jolt".

Hence, according to the passage, there would be only one explicitly mentioned way to "eliminate the jolt".

C. There are at least two different forces acting upon the racket.

In my opinion, the specific fragment that is quoted as providing proof for this statement is actually giving reasons to question it.
 
The impact of the ball would cause the racket to bounce backwards, experiencing a translational motion away from the ball. The tendency of this motion would be to jerk all parts of the racket, including the end of its handle, backward, or away from the ball. Unless the ball happened to hit the racket precisely at the racket's center of mass, the racket would additionally experience a rotational motion around its center of mass-much as a penny that has been struck near its edge will start to spin.

While I agree that in majority of cases, the fragment clearly states that two forces are exerted on the racket. However, there seems to be an exception - "unless the ball happened to hit the racket precisely at the racket's center of mass, the racket would additionally experience a rotational motion...". In my opinion, this suggests that there is one instance when only one force is exerted on the racket which would make this answer questionable, especially in view of imperfect answer A.

Happy to discuss if you disagree with this reasoning.

gmatlover12 · Answer

For the second question, I am convinced option D is correct. Please chime in with your counter-opinions.

Counterargument to OA (option A) - centre of percussion seems to eliminate the jolt/strain. The other sweet spot greatly reduces the strain, but does not eliminate. This has also been reiterated in another reply above.

No one has yet spoken about Option D though. "The end of the handle of the racket will jerk forward after striking the ball unless the ball
strikes the racket;s center of mass". Not really. If the ball does not hit the centre of mass, both translational and rotational forces apply, and the racket could jerk forward or backward depending on which force dominates (last line para 2) IF it hits at the centre of mass, then translational force is zero; therefore racket definitely jerks forwards. Either way, option D is untrue. Hence, the correct answer.

JT93 · Answer

Hey guys,

Can someone help me understand why my thinking is off?

For Q3, I ruled out choice (B) and chose answer (E) instead because I thought:
(B) to provide an explanation of the mechanics of the phenomenon discussed in the passage -> I thought this was wrong because I thought "the mechanics" was referring to the second sweet spot which was explained in Paragraph 3

(E) to explain why the main idea of the passage would be useful for tennis players -> I thought this was right because the physics explained in Paragraph 2 was important to understand why the physics of the sweet spot in Paragraph 3 was important

Thanks in advance!

bM22 · Answer

Hi  JT93 ,

It is true that "the mechanics" discussed in the passage is referring to the second sweet spot discusses in the 3rd para, but the 2nd para serves as an explanation for the impact between the ball and the racket. It helps in setting a basic understanding about "impacts", for the second sweet spot, when author mentions: "there is one point of impact, known as the center of percussion, which causes neither motion to predominate,", with both impacts being having been discussed earlier and how a center of percussion spot has none.

Option E is incorrect, as the passage is mostly about the center of percussion and the impacts it has or doesn't, whether it's useful for tennis players or not is not the main concern.

Let me know if you still have doubts.
Thanks.

rishab0507 · Answer

carcass  , For Q 5, Option C: Author is talking about 2 spots in this para, Node and center of percurssion. Option C mentions only 1 , ignoring the first sweet spot. So if we consider 1st one, center of percussion is not he only way, making Option C fall apart. How it can be correct one

bM22 · Answer

Hi  rishab0507 ,

Let me know if this helps.

Option C : 
can be inferred from the lines: "many players are unaware of the existence of a second, lesser-known location on the racket face, the center of percussion,  that will also greatly diminish the strain on a player's arm when the ball is struck .".
C says that striking a tennis ball at a spot other than the center of percussion can result,  not will result in a jarring feeling . This leaves a window open for the 1st sweet spot as well. Author is not denying or rejecting the 1st sweet spot, he is simply saying that the2nd sweet spot can also diminish strain on player's arm to a great extent.

Thanks.

gmatway · Answer

Hi, Below is my explanation

structure of passage -
para 1 - intro of secondary sweet spot 
para2 - mechanism of sweet spot 
para3 - why our sweet spot is so special 
para 4 - how to discover /experience sweet spot on your racket.

REMEMBER TO CHOOSE BEST ANSWER WE NEED EVIDENCE!

1. What is the primary message the author is trying to convey?

(A) a proposal for an improvement to the design of tennis rackets
(B) an examination of the differences between the two types of sweet spot
(C) a definition of the translational and rotational forces acting on a tennis racket
(D) a description of the ideal area in which to strike every ball
 (E) an explanation of a lesser-known area on a tennis racket that dampens unwanted vibration - correct, author is writing this passage to inform us about this second sweet spot . usae of though clears our doubt that sweet spot is not the main idea of the passage but SECOND sweet spot is ! . refer lines para1 - 'Though most tennis players generally strive to strike the ball on the racket's vibration node, more commonly known as the "sweet spot," many players are unaware of the existence of a second, lesser-known location on the racket face, the center of percussion'

chris139  
2. According to the passage, all of the following are true of the forces acting upon a tennis racket striking a ball EXCEPT

THE ONLY OPTION THAT IS NOT TRUE IS BOLD ONE 
 (A) The only way to eliminate the jolt that accompanies most strokes is to hit the ball on the center of percussion.- correct.the iven lines in para 1 mentions 'WILL ALSO ' which means sweep spot also reduces the strain HENCE second sweet spot is NOT THE ONLY FORCE as mentioned in A . refer lines - 'many players are unaware of the existence of a second, lesser-known location on the racket face, the center of percussion, that will also greatly diminish the strain on a player's arm when the ball is struck.'  
(B) The impact of the ball striking the racket can strain a tennis player's arm.
(C) There are at least two different forces acting upon the racket.
(D) The end of the handle of the racket will jerk forward after striking the ball unless the hall strikes the racket's center of mass.
(E) The racket will rebound after it strikes the ball.

3. What is the primary function served by paragraph two in the context of the entire passage?

(A) to establish the main idea of the passage
 (B) to provide an explanation of the mechanics of the phenomenon discussed in the passage - correct . the lines 'In order to understand the physics of this second sweet spot,' 
(C) to introduce a counterargument that elucidates the main idea of the passage
(D) to provide an example of the primary subject described in the passage
(E) to explain why the main idea of the passage would be useful for tennis players

4. The author mentions "a penny that has been struck near its edge" in order to

(A) show how the center of mass causes the racket to spin
(B) argue that a penny spins in the exact way that a tennis racket spins
(C) explain how translational motion works
 (D) provide an illustration of a concept . correct . the usage of 'AS' ...author mentioned the analogy to illustrate what it would spin like. refer lines ' the racket would additionally experience a rotational motion around its center ' 
(E) demonstrate that pennies and tennis rackets do not spin in the same way

5. Which of the following can be inferred from the passage?

(A) If a player holds the tennis racket anywhere other than the end of the handle, the player will experience a jolting sensation. (no evidence)
(B) The primary sweet spot is more effective at damping vibration than the secondary sweet spot.
 (C) Striking a tennis ball at a spot other than the center of percussion can result in a jarring feeling. - Refer lines 3rd para & last para last lines 'When the player strikes the ball at the center of percussion, her wrist is jerked neither forward nor backward, and she experiences a relatively smooth, comfortable tennis stroke.' + 'If the handle jumps out of your hand, then the ball has missed the center of percussion.'   
(D) Striking a tennis ball repeatedly at spots other than a sweet spot leads to "tennis elbow."
(E) If a player lets go of the racket at the moment of impact, the simultaneous forward and backward impetus causes the racket to drop straight to the ground.

Aryabhatta2me · Answer

@brailLab
I am not convinced with the answer of question 5. 
two options I am struggling with 
(C) Striking a tennis ball at a spot other than the center of percussion can result in a jarring feeling.
(D) Striking a tennis ball repeatedly at spots other than a sweet spot leads to "tennis elbow."
option C -is correct and indeed possible to find in the passage as well --- but it says other than COP can result in Jarr feeling.. what if it hits the Center of Mass then definitely it will give the same effect as CO. Percussion. so how can we say that's a correct answer.
on the other hand for option D
yes, there is nowhere given about the "TENNIS ELBOW" but we can find that it will create vibration and strain ,.. which will ultimately cause the " tennis elbow" so we indeed can infer this from passage.... infrence not required to match word by word.... there is difference b/w question of " inference type " and " following can be found in the passage type " question.

VIBHOJAIN · Answer

Hi  MartyMurray 
Can you please explain last question of this paragraph. I chose option A because it is mentioned int he 1st para that there are 2 sweet psots.
If there are 2 sweet spots then how can it support option C?

axeofflane · Answer

Question 2, why cant the answer be E?
The tennis racket wont ALWAYS rebound if it hits the ball right, what if it hits the centre of percussion?

Or are they trying to say that the only reason its not rebounding is cause of player force

Though most tennis players generally strive to strike the ball on the

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Reading Comprehension (RC) Questions

Though most tennis players generally strive to strike the ball on the

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards