Merge branch 'master' of https://github.com/openwebwork/webwork-open-…

…problem-library

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-001.pg

@@ -65,16 +65,16 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-Consider a two-material beam consisting of bone and stainless steel that is subjected to axial loading of [`[$P]`] [`N`]. Given that
+A beam consisting of two materials (bone (component 1) and stainless steel (component 2)) is loaded with an axial force of [`[$P]`] [`N`]. If the properties and areas are:
 
 E1 = [`[$E1]`] [`GPa`]
 E2 = [`[$E2]`] [`GPa`]
 A1 = [`[$A1]`] [`mm^2`]
 A2 = [`[$A2]`] [`mm^2`]
 
-what is the portion of the load carried by component 1 (bone)?
+what percentage of the load is carried by component 1 (bone)?
 
-[`Portion=`] [_____]{"$portion"} [`%`]  
+[`Load carried by bone=`] [_____]{"$portion"} [`%`]  
 
 END_PGML
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-004.pg

@@ -61,8 +61,8 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-The average horizontal velocity of a penalty kick in soccer is [`[$v]`]
- [`m/s`]. The hoizontal displacement of the ball from the kicker's foot to the goal is [`[$disp]`] [`m`]. How long does it take for the ball to reach the goal after it is kicked?
+The average horizontal velocity of a penalty kick in soccer (football) is [`[$v]`]
+ [`m/s`]. The horizontal distance travelled by the ball between the player's foot and the goal is [`[$disp]`] [`m`]. How many seconds does it take the ball to travel between the player's foot and the goal?
 
  [`t=`] [_____]{"$dt"} [`s`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-015.pg

@@ -61,7 +61,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-The sweet spot on a baseball bat is [`[$ss]`] [`cm`] from the axis of rotation during the swing of the bat. If this sweet spot moves at [`[$v]`] [`m/s`], how fast is the angular velocity of the bat?
+The ideal spot for the ball to contact a baseball bat is [`[$ss]`] [`cm`] from the axis of rotation of the swinging bat. If this ideal location is moving at a speed of [`[$v]`] [`m/s`], what is the angular velocity of the bat?
 
 [`\omega=`] [_____]{"$omega"} [`rad/s`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-018.pg

@@ -74,7 +74,7 @@ BEGIN_PGML
 
 [@ image("UBC-BME-18-018.png", width=>[$width], height=>[$height]) @]*
 
-The quadriceps pulls on the patella with a force of [`F=[$F]`] [`N`] while the patellar tendon pulls on the patella with a force of [`F=[$F]`] [`N`] also. The knee is in a flexed position, so the angle between these two forces is [`\theta=[$theta]^{\circ}`]. A compressive force from the femoral condyles is the only other significant force acting on the patella. If the patella is in static equilibrium,  how large is the compressive force, [`F_c`], exerted by the femoral condyles on the patella?
+If the force in the quadriceps tendon acting on the patella is [`F=[$F]`] [`N`] assume that the patellar tendon also acts on the patella with a force of [`F=[$F]`] [`N`]. When the knee is in a flexed position, the angle between these two forces is [`\theta=[$theta]^{\circ}`]. A normal contact force on the patella from the femoral condyles is the only other significant patellar force. If the patella is in static equilibrium, find the contact force, [`F_c`], exerted by the femoral condyles on the patella.
 
 [`F_c=`] [_____]{"$Fc"} [`N`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-019.pg

@@ -75,7 +75,7 @@ BEGIN_PGML
 
 [@ image("UBC-BME-18-019.png", width=>[$width], height=>[$height]) @]*
 
-Brian is trying to pull Julie on a sled across a flat, snowy field. Brian pulls on a rope attached to the sled. His pulling force is directed forward and upward at an angle of [`\theta=[$theta]^{\circ}`] above horizontal. Julie's mass is [`[$mj]`] [`kg`], and the sled's mass is [`[$ms]`] [`kg`]. If the coefficient of static friction between the sled runners and the snow is [`[$mu]`], how much force must Brian exert on the rope to start moving the sled?
+Student A wants to start pulling Student B on a sled across a flat and snow-covered field. Student A pulls on a rope attached to the sled. The pulling force acts at an angle of [`\theta=[$theta]^{\circ}`] above horizontal. Student B's mass is [`[$mj]`] [`kg`], and the mass of the sled is [`[$ms]`] [`kg`]. If the coefficient of static friction between the sled and the snow is [`[$mu]`], find the force that Student A must exert to overcome friction and start moving the sled.  
 
 [`F=`] [_____]{"$F"} [`N`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-024.pg

@@ -77,13 +77,13 @@ BEGIN_PGML
 
 [@ image("UBC-BME-18-024.png", width=>[$width], height=>[$height]) @]*
 
-Louise spikes a volleyball. At the instant the ball leaves her hand, its height is [`h=[$h]`] [`m`] and its resultant velocity is [`v=[$v]`] [`m/s`] downward and forward at an angle of [`\theta=[$theta]^{\circ}`] below horizontal.
+A played spikes a volleyball (that is, hits it such that it moves downward). At the instant it leaves the player's hand, the ball is [`h=[$h]`] [`m`] above the ground and has a resultant velocity of [`v=[$v]`] [`m/s`] directed downward and forward ([`\theta=[$theta]^{\circ}`] below horizontal). Assume that the opposing team is unable to block the ball before it hits the floor. 
 
-*a)* How long will it take for the ball to strike the floor if the opposing team does not block it?
+*a)* How many seconds will it take the ball to hit the floor?
 
 [`t=`] [_____]{"$t"} [`s`]  
 
-*b)* How far will the ball travel horizontally before it strikes the floor?
+*b)* How far will the ball travel in the x-direction (horizontally) before it hits the floor?
 
 [`\Delta x=`] [_____]{"$dx"} [`m`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-025.pg

@@ -63,13 +63,13 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-Chloe has a vertical velocity of [`[$v]`] [`m/s`] when she leaves the [`1`] [`m`] diving board. At this instant, her center of gravity is [`[$cog]`] m above the water.
+A diver has a vertical velocity of [`[$v]`] [`m/s`] when they leave the [`1`] [`m`] diving board (that is, the surface of the board is [`1`] [`m`] above the water). At this instant, the diver's centre of gravity is [`[$cog]`] m above the water.
 
-*a)* How high will Chloe's center of gravity go?
+*a)* What is the maximum height the diver's centre of gravity will reach? ?
 
 [`y_{peak}=`] [_____]{"$h"} [`m`]  
 
-*b)* How long will Chloe be in the air before she touches the water? Assume that she first touches the water when her center of gravity is [`1`] [`m`] above the water.
+*b)* How long will the diver be in the air before they initially enter the water? Assume that the diver initially enters the water when their centre of gravity is [`1`] [`m`] above the water.
 
 [`t=`] [_____]{"$t"} [`s`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-036.pg

@@ -66,13 +66,13 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-Maddie is standing still when her dancing partner, Paul, begins to lift her up and throw her into the air. Maddie's mass is [`[$m]`] [`kg`]. Paul exerts an average vertical force of [`[$f]`] [`N`] for [`[$t]`] [`s`] on Maddie during the lift and throwing motion.
+An ice dancer is standing still when her partner starts to lift her up and throw her into the air. The ice dancer's mass is [`[$m]`] [`kg`]. The partner exerts an average vertical force of [`[$f]`] [`N`] for [`[$t]`] [`s`] on the lifted dancer during this motion.
 
-*a)* What is Maddie's vertical velocity when Paul releases her?
+*a)* What is the lifted ice dancer's vertical velocity when her partner releases her?
 
 [`v=`] [_____]{"$v"} [`m/s`]  
 
-*b)* If Maddie's center of gravity was [`[$cog]`] [`m`] above the floor when Paul released her, what peak height will she reach?
+*b)* If the centre of gravity of the lifted ice dancer was [`[$cog]`] [`m`] above the floor when released, what is the maximum height will she reach?
 
 [`y_{peak}=`] [_____]{"$h"} [`m`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-040.pg

@@ -70,29 +70,29 @@ tolerance=>.01);
 BEGIN_PGML
 
 
-A gymnast falls from the high bar and lands on a [`[$t]`] [`cm`] thick gymnastics mat. The gymnast strikes the back of his head against the mat during his landing. His head is moving at [`[$v]`] [`m/s`] when it first strikes the mat. The mass of his head is [`[$m]`] [`kg`]. The impact ends when the gymnast's head comes to a stop after deflecting the mat [`[$dt]`] [`cm`]. Hint: don't forget potential energy and pay attention to direction!
+A gymnast falls from the rings and strikes the back of their head on a [`[$t]`] [`cm`] thick gymnastics mat. When it first strikes the mat, the [`[$m]`] [`kg`] head is moving at [`[$v]`] [`m/s`]. Assume that the impact ends when the gymnast's head stops moving after deflecting the mat [`[$dt]`] [`cm`]. Hint: consider potential energy and be careful about directions.
 
-*a)* How much kinetic energy does the gymnast's head have at the instant just before it contacts the mat?
+*a)* How much kinetic energy does the gymnast's head have just before hitting the mat?
 
 [`KE=`] [_____]{"$ke"} [`J`]  
 
-*b)* How much work does the mat do to stop the motion of the gymnast's head?
+*b)* How much work does the mat do to stop the gymnast's head?
 
 [`W=`] [_____]{"$w"} [`J`]  
 
-*c)* What average impact force does the mat exert on the gymnast's head during the impact?
+*c)* What is the average impact force exerted on the gymnast's head during the impact?
 
 [`F=`] [_____]{"$f"} [`F`]  
 
-*d)* Estimate the peak impact force exerted by the mat on the gymnast's head. You can assume a triangular loading profile.
+*d)* Estimate the peak impact force exerted on the gymnast's head by the mat . Assume a triangular loading profile.
 
 [`F_{peak}=`] [_____]{"$fp"} [`F`]  
 
 *e)* Estimate the peak acceleration of the gymnast's head.
 
 [`a_{peak}=`] [_____]{"$ap"} [`m/s^2`]  
 
-*f)* Express this peak acceleration in g's.
+*f)* Express the peak acceleration you found above in g's.
 
 [`a_{peak}=`] [_____]{"$apg"} [`g`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-043.pg

@@ -24,8 +24,8 @@ DOCUMENT();
 $imgScale = .4;
 
 #image aspect ratio
-$width = $imgScale*1477;
-$height = $imgScale*580;
+$width = $imgScale*4373;
+$height = $imgScale*1667;
 
 loadMacros(   
 	"PGstandard.pl",     # Standard macros for PG language
@@ -72,7 +72,7 @@ BEGIN_PGML
 
 [@ image("UBC-BME-18-043.png", width=>[$width], height=>[$height]) @]*
 
-A pole-vaulter is holding a vaulting pole parallel to the ground. The pole is [`5`] [`m`] long. The vaulter grips the pole with his right hand [`10`] [`cm`] from the top end of the pole and with his left hand [`1`] [`m`] from the top end of the pole. Although the pole is quite light (its mass is only [`[$m]`] [`kg`]), the forces that the vaulter must exert on the pole to maintain it in this position are quite large. How large are they? (_Assume that the vaulter exerts only vertical-up or down-forces on the horizontal pole and that the center of gravity of the pole is located at the center of its length._)
+A pole-vaulter is holding a [`5`] [`m`] long vaulting pole parallel to the ground. The vaulter's hands both grip the pole, with the right hand [`10`] [`cm`] from the top end and the left hand [`1`] [`m`] from the top end. Although the pole is quite light (its mass is only [`[$m]`] [`kg`]), the vaulter must exert substantial forces on the pole to maintain it in this position. How large are they? (_Assume that the vaulter's hands exert only vertical forces on the horizontal pole and that the center of gravity of the pole is located halfway down its length._)
 
 [`F_{Right}=`] [_____]{"$fr"} [`N`]  
 [`F_{Left}=`] [_____]{"$fl"} [`N`]  

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-045.pg

@@ -64,21 +64,21 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-A [`[$m]`] [`kg`] gymnast holds an iron cross position on the rings. In this position, the gymnast's arms are abducted [`90^{\circ}`] and his trunk and legs are vertical. The horizontal distance from each ring to the gymnast's closest shoulder is [`[$d]`] [`m`]. The gymnast is in static equilibrium.
+A gymnast, mass [`[$m]`] [`kg`], holds a static iron cross position on the rings. In this position, the gymnast's arms are abducted [`90^{\circ}`] while the gymnast's trunk and legs are vertical. The horizontal distance from each ring to the shoulder of the arm holding that ring is [`[$d]`] [`m`]. 
 
-*a)* What vertical reaction force does each ring exert on each hand?
+*a)* What is the vertical component of the reaction force exerted on each hand by the ring?
 
 [`F_R=`] [_____]{"$fr"} [`N`]  
 
-*b)* What torque is exerted by the right ring about the right shoulder joint?
+*b)* What torque is exerted about the right shoulder joint by the right ring?
 
 [`T=`] [_____]{"$t"} [`Nm`]  
 
-*c)* How much torque must the right shoulder adductor muscles produce to maintain the iron cross position?
+*c)* How much torque must the right shoulder adductor muscles produce to maintain this static position?
 
 [`T=`] [_____]{"$t"} [`Nm`]  
 
-*d)* If the moment arm of the right shoulder adductor muscles about the shoulder joint is [`[$r]`] [`cm`], how much force must these muscles produce to maintain the iron cross?
+*d)* If the right shoulder adductor muscles have a moment arm of [`[$r]`] [`cm`] about the shoulder joint, how much force must these muscles produce to maintain the iron cross?
 
 [`F_m=`] [_____]{"$fm"} [`N`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-047.pg

@@ -61,7 +61,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-Becky is sparring in a Tae Kwon Do class. Her opponent executes a roundhouse kick. The average angular velocity of his kicking leg and foot is [`[$omega]`] [`rad/s`]. The angular displacement of his foot to Becky's head is [`[$theta]`] [`rad`]. How much time does Becky have to move if she wants to avoid being kicked in the head?
+An athlete executes a roundhouse kick in Tae Kwon Do. The average angular velocity of the kicking leg and foot is [`[$omega]`] [`rad/s`]. The angular displacement of the foot to the opponent's head is [`[$theta]`] [`rad`]. How much time does the opponent have to move out of the path of the kick to avoid a blow to the head?
 
 [`t=`] [_____]{"$t"} [`s`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-048.pg

@@ -62,7 +62,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-The tendon from Lissa's knee extensor muscles attaches to the tibia bone [`[$t]''`] below the center of her knee joint, and her foot is [`[$f]''`] away from her knee joint. What arc length does Lissa's foot move through when her knee extensor muscles contract and their point of insertion on the tibia moves through an arc length of [`[$d]''`]?
+For one person, the tendon of the knee extensor muscles attaches to the tibia [`[$t]''`] below the center of the knee joint. The foot is [`[$f]''`] away from her knee joint. What arc length does the foot move through when the knee extensor muscles contract and the insertion point on the tibia moves through an arc length of [`[$d]''`]?
 
 [`l=`] [_____]{"$l"}[`''`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-050.pg

@@ -62,7 +62,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-A hook in boxing primarily involves horizontal flexion of the shoulder while maintaining a constant angle at the elbow. During this punch, the horizontal flexor muscles of the shoulder contract and shorten at an average speed of [`[$v]`] [`cm/s`]. They move through an arc length of [`[$l1]`] [`cm`] during the hook, while the fist moves through an arc length of [`[$l2]`] [`cm`]. What is the average speed of the fist during the hook?
+A boxing hook involves horizontal flexion of the shoulder while maintaining a constant angle at the elbow. During this punch, the shoulder horizontal flexor muscles shorten at an average speed of [`[$v]`] [`cm/s`]. The shoulder flexors move through an arc length of [`[$l1]`] [`cm`] during the hook, while the fist moves through an arc length of [`[$l2]`] [`cm`]. Find the average speed of the fist during the hook. 
 
 [`v=`] [_____]{"$v2"} [`m/s`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-051.pg

@@ -94,13 +94,13 @@ BEGIN_PGML
 
 [@ image("UBC-BME-18-051.png", width=>[$width], height=>[$height]) @]*
 
-A baseball pitcher pitches a fastball with a horizontal velocity of [`[$v]`] [`m/s`]. The horizontal distance from the point of release to home plate is [`L=[$l]`] [`m`]. The batter decides to swing the bat [`[$t]`] [`s`] after the ball has been released by the pitcher. The average angular velocity of the bat is [`[$omegaave]`] [`rad/s`]. The angular displacement of the bat from the batter's shoulder to hitting positions above the plate is between [`1.5`] and [`1.8`] [`rad`].
+A fastball has a horizontal velocity of [`[$v]`] [`m/s`], and is released a horizontal distance of [`L=[$l]`] [`m`] from home plate. The batter swings the bat [`[$t]`] [`s`] after the ball has been released. The bat has an average angular velocity of [`[$omegaave]`] [`rad/s`]. The bat must rotate between [`1.5`] and [`1.8`] [`rad`] from the batter's shoulder to hitting positions above the plate.
 
-*a)* Will the bat be in a hitting position above the plate when the ball is above the plate? Assume the pitch is in the strike zone.
+*a)* Will the bat be in a hitting position above the plate when the ball is above the plate? Assume the pitch is directed such that it comes in over the plate.
 
 [@ $mcCorrect-> menu() @]*
 
-*b)* Assume that the batter does hit the ball. If the bat's instantaneous angular velocity is [`[$omegains]`] [`rad/s`] at the instant of contact, and the distance from the sweet spot on the bat to the axis of rotation is [`[$ss]`] [`m`], what is the instantaneous linear velocity of the sweet spot at the instant of ball contact?
+*b)* Assume that the batter connects with the ball. If the instantaneous angular velocity of the bat at contact is [`[$omegains]`] [`rad/s`], and the distance between the sweet spot (ideal contact location) on the bat and the axis of rotation is [`[$ss]`] [`m`], find the linear velocity of the sweet spot when it connects with the ball.
 
 [`v=`] [_____] [`m/s`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-058.pg

@@ -62,7 +62,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-A [`[$l]`] [`cm`] long section of the patellar ligament stretches to [`[$dl+$l]`] [`cm`] when it is subjected to a tensile force of [`[$f]`] [`N`]. What is the strain in this segment of ligament?
+A sample of patellar ligament that is initially [`[$l]`] [`cm`] long stretches to [`[$dl+$l]`] [`cm`] when a tensile force of [`[$f]`] [`N`] is applied. Find the strain in this ligament sample?
 
 [`\epsilon=`] [_____]{"$eps"} [`%`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-059.pg

@@ -61,7 +61,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-The modulus of elasticity (for compression) for a section of compact bone in the femur is [`[$e]`] [`GPa`]. If this bone is subjected to a compression stress of [`[$p]`] [`MPa`], what strain results from this compression?
+The modulus of elasticity (for compression) for compact bone in the femur is [`[$e]`] [`GPa`]. Find the strain that results from applying a compressive stress of [`[$p]`] [`MPa`] to this bone sample. 
 
 [`\epsilon=`] [_____]{"$eps"} [`%`]
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-060.pg

@@ -61,7 +61,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-The Achilles tendon is subjected to a large tension stress that results in a strain of [`[$eps]%`]. If the unloaded tendon is [`[$l]`] [`cm`] long, how much does it elongate as a result of this strain?
+A sample Achilles tendon is subjected to a large tensile stress that results in a strain of [`[$eps]%`]. If the unloaded tendon is [`[$l]`] [`cm`] long, find the change in length (in cm) due to the applied tensile stress.  
 
 [`\Delta l=`] [_____]{"$dl"} [`cm`]  
 

Contrib/UBC/BMEG/Mechanics/UBC-BME-18-061.pg

@@ -64,7 +64,7 @@ tolerance=>.01);
 
 BEGIN_PGML
 
-The modulus of elasticity for a prosthetic material is [`[$e]`] [`GPa`]. A [`[$l]`] [`cm`] long sample of this material is circular in cross section with a radius of [`[$r]`] [`cm`]. This sample is stretched [`[$l+$dl]`] [`cm`]. What tensile force was applied to the material to create this stretch?
+A prosthetic material has a modulus of elasticity of [`[$e]`] [`GPa`]. Consider a [`[$l]`] [`cm`] long sample of this material of circular cross-section (radius [`[$r]`] [`cm`]). This sample is stretched [`[$l+$dl]`] [`cm`]. Find the tensile force needed to create this elongation. 
 
 [`F=`] [_____]{"$f"} [`N`]