Physics Test-#2 (12/11-12/12)
What is VECTOR SUBTRACTION?
-(graphically) the negative of any vector that has the same magnitude, but points in the OPPOSITE direction
The magnitude of the horizontal velocity of a projectile is always...? (MOP-VP8)
-CONSTANT
What are some examples of vector quantities?
-DISPLACEMENT, VELOCITY, ACCELERATION
The acceleration of a projectile is always directed...? (MOP-VP8)
-DOWNWARD
TRUE OR FALSE: A projectiles acceleration is always directed upward (MOP-VP8)
-FALSE! It is always directed DOWNWARD
TRUE OR FALSE: The V(y) is directed DOWNWARD as a projectile is moving upward and is directed UPWARD as it is falling (MOP-VP8)
-FALSE! It is directed UPWARD as it is moving up and DOWNWARD as it is falling
TRUE OR FALSE: The horizontal velocity of a projectile is changing (MOP-VP8)
-FALSE! The horizontal velocity of a projectile is NOT CHANGING; the vertical velocity changes, not horizontal!
TRUE OR FALSE: A boat heads straight across a rive. the river flows north at a speed of 3 m/s. If the river current was greater, then the time required for the boat to reach the opposite shore would be less. (MOP-VP6)
-FALSE!!!!! River current doesn't effect time!!!
The magnitude of the VERTICAL velocity of a projectile is ALWAYS what? (MOP-VP8)
-IT IS ALWAYS CHANGING
The magnitude of the horizontal velocity of a projectile is ALWAYS what? (MOP-VP8)
-IT IS ALWAYS CONSTANT
a boat begins at point A and heads straight across a 60 meter wide river with a speed of 4 m/s (relative to the water). The river water flows north at a speed of 3 m/s (relative to the shore). The boat reaches the opposite shore art point C. What would cause the boat to reach the opposite shore at a location NORTH of C? (MOP-VP6)
-If the river flows north at 2 m/s instead of 3 m/s -if the boat heads across the river at 3 m/s instead of 4 m/s
On a level tabletop is a ruler&on the ruler is a tiny beetle. The beetle, relative to the ruler, is crawling to the left. But a little boy is pulling the ruler to the right, at a speed larger than the beetle's speed relative to the ruler. What can you say about the speed of the beetle RELATIVE TO THE TABLE TOP? (QUEST #10)
-It is less than the speed of the ruler
What are some examples of scalar quantities?
-LENGTH, area, volume, mass, TEMPERATURE, SPEED
When does the acceleration of a projectile have the greatest magnitude? (MOP-VP8)
-NEVER because it is CONSTANT!! It is always the same
Does the HORIZONTAL velocity [V(x)] of a projectile change?
-NO!!!! It remains constant
When a problem has to do with SPEED, do you need to specify the direction?
-NO, because it is a SCALAR quantity
What SHAPE is projectile motion? (*test question*)
-PARABOLIC
Which of the following is a physical quantity that had magnitude but no direction: vector, scalar, resultant, component (QUIZ QUESTION)
-Scalar
TRUE OR FALSE: A projectile's acceleration is a constant value (MOP-VP8)
-TRUE!
TRUE OR FALSE: the V(y) value is 0 m/s at the peak of a projectile's trajectory (MOP-VP8)
-TRUE!
TRUE OR FALSE: The V(y) value is changing by 9.8 m/s every second (MOP-VP8)
-TRUE!!
A projectile is launched horizontally with a velocity of 60 m/s. After 3 seconds, the magnitude of the HORIZONTAL component of velocity is approximately _______ m/s and the magnitude of the VERTICAL component of velocity is approximately _____ m/s. (MOP-VP9)
-The HORIZONTAL velocity is approx. 60 m/s -the VERTICAL velocity is approx. 30 m/s
Two cars travel towards one another. Car A travels at a speed of 30 mph to the right (the positive x direction). Car B travels at 10 mph to the left. Let V(ab) be the velocity of car A as seen by the driver of car B (i.e. The velocity of A relative to B). V(ab) is the velocity of B relative to A. What is V(ab) and V(ba)? (QUEST #10)
-V(ab)=40 mph -V(ba)=-40 mph
Is 2-D motion scalar or vector?
-VECTOR; you MUST specify direction relative to some reference frame or coordinate system -ex: 55 mph at 30 degrees South of East
Which of the following is an example of a vector quantity: velocity, temperature, volume, mass (QUIZ QUESTION)
-Velocity
Which of the following is not an example of projectile motion? (EBACKPACK QUIZ)
-a hot-air balloon drifting toward Earth
What is a COMPONENT?
-a piece of vector that points in either the vertical or horizontal direction (projections of a vector onto the axis) -resolving vectors into components
When using the Pythagorean theorem, what MUST you have?
-a right triangle
What is the ANALYTICAL METHOD?
-a way of determining the magnitude and direction of a resultant vector using the Pythagorean theorem and trig identities
Which of acceleration, age, speed, temperature and velocity are vector quantities? (QUEST question)
-acceleration and velocity
How can every vector be expressed?
-as the sum of its horizontal and vertical components
A 3-kg projectile is launched upward and rightward from ground level. The magnitude of the ACCELERATION of the 3-kg projectile at the PEAK of its trajectory is ______ m/s/s. (MOP-VP8)
-at the peak, the acceleration is approximately 10 m/s/s
Vector A is resolved into 2 components: -A(x) and A(y). If the two components are added together in head-to-tail fashion, then the resultant would...? (MOP-VP5)
-be the original vector
What is VECTOR ADDITION?
-commutative (the order added doesn't effect the final sum)
Vector components are important in physics because they describe the...? (MOP-VP5)
-effect of a vector in a given direction
Vector components are important in physics because they describe the...? (QUIZ QUESTION)
-effect of a vector in a given direction
You are throwing a ball for the second time. If the ball leaves your hand with twice the velocity it had on your first throw, its horizontal range R (compared to your first serve) would be...(EBACKPACK QUIZ)
-four times as much
If vectors are moved according to the rules of the head-to-tail method of vector addition, then the resultant vector is drawn...(QUIZ QUESTION)
-from the tail of the first vector to the head of the last vector
When a vector diagram is used to add 3 vectors using the head-to-tail method, the resultant is drawn with a specific direction and orientation. The proper direction for drawing the resultant is...(MOP question)
-from the tail of the first vector to the head of the last vector
When a vector diagram is used to add 3 vectors using the head-to-tail method, the resultant is drawn with a specific direction and orientation. The proper direction for drawing the resultant is...? (MOP-VP2)
-from the tail of the first vector to the head of the last vector
What methods do you use for VECTOR ADDITION?
-head-to-tail method (the graphical way to add vectors); limited in accuracy (bc drawings can be off sometimes)
You are trying to cross a river that flows due south with a strong current. You start out in your motorboat on the east bank desiring to reach the West Bank directly west from your starting point. You should head your motorboat...(EBACKPACK QUIZ)
-in a northwesterly direction
When using the HEAD-TO-TAIL METHOD, how many vectors can you use?
-it is valid for an amount/number of vectors (You can have a, b, c, d, e etc. as many as you want/need)
A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity does what? (EBACKPACK QUIZ)
-it remains constant
In a diagram, the length of a vector arrow represents the...? (QUIZ QUESTION)
-magnitude of the vector
What is RANGE?
-maximum HORIZONTAL distance that a projectile travels
The horizontal velocity of a projectile is changing because...? (MOP-VP8)
-nonsense!! The horizontal velocity of a projectile is NOT changing!!
The components of a vector are...? (QUIZ QUESTION)
-perpendicular to each other
What is a "FRAME OF REFERENCE"?
-perspective from which changes in position are being measured
Vector components might be best defined as the...? (MOP-VP5)
-projection of a vector onto an axis
What is a VECTOR quantity?
-quantity with BOTH direction and magnitude
What is a SCALAR quantity?
-quantity with magnitude but NO direction
ignoring air resistance, the horizontal component of a projectile's acceleration...(EBACKPACK QUIZ)
-remains a non-zero constant
The vector sum of two or more vectors is known as the....? (QUIZ QUESTION)
-resultant
Is "the speed of a snail" vector or scalar? (QUIZ QUESTION)
-scalar
Is "the time it takes to run a mile" vector or scalar? (QUIZ QUESTION)
-scalar
The acceleration of gravity on the Moon is only one-sixth of that on Earth. If you hit a baseball on the Moon with the same effort (and at the speed and angle) that you would on Earth, the ball would land...(EBACKPACK QUIZ)
-six times as far
A piece of chalk is dropped by a teacher walking at a speed of 1.5 m/s. From the teacher's perspective, the chalk appears to fall...(EBACKPACK QUIZ)
-straight down
At the peak of a projectile what can you always assume?
-that VELOCITy=0 m/s (because its at its turning point), BUT there is STILL horizontal velocity
A projectile is launched horizontally. As it travels along its trajectory toward the ground, the HORIZONTAL component of its velocity _______ and the VERTICAL component of its velocity ______ (MOP-VP9)
-the HORIZONTAL component REMAINS THE SAME -the VERTICAL component INCREASES as it travels towards the ground
A boat begins at point A and heads straight across a river. because of the 2 m/s river current, the boat lands on the opposite shore at point C. If the river current was 1 m/s, then the boat would land on the opposite shore at what location....? (Assume that the boat speed relative to the water does not change) (MOP-VP6)
-the boat would land at a location SOUTH of C
A child aims his air rifle at an angle of 10 degrees above the horizontal. He fires a b-b while simultaneously dropping another b-b from rest, from the same height as the rifle barrel. Which b-b will hit the ground first? (QUEST #11)
-the dropped b-b
When giving directions to your house, you tell someone to drive 2 miles east, then 3 miles north, then 1 mile west. What are the components of a vector that points from his house to yours? (MOP question)
-the east component of the vector is 1 mile ; the north component is 3 miles
What does a component describe?
-the effect of a vector in a given direction
What is the HEAD OF A VECTOR?
-the end point of a vector (the tip of the arrow head)
What is INDEPENDENCE OF MOTION?
-the horizontal and vertical components of 2D motion are independent of each other -ANY motion in the horizontal direction does not affect motion in the vertical direction and vice versa
A projectile is launched upward at an angle to the horizontal. The initial HORIZONTAL velocity is 30 m/s; the initial VERTICAL velocity is 50 m/s. After 4 seconds, the magnitude of the HORIZONTAL component of velocity is approx. _____ m/s and the magnitude of the VERTICAL component of velocity is approx. _____ m/s (MOP-VP9)
-the initial magnitude of the HORIZONTAL velocity is approx. 30 m/s -the initial magnitude of the VERTICAL velocity is approx. 10 m/s
What is PROJECTILE MOTION?
-the motion of an object that is subject only to the acceleration of gravity
If you are standing in a bus that moves at constant velocity and drop a ball rom your outstretched hand, you will see its path as a vertical straight line. How will the path appear to a friend standing at the side of the road? (QUEST #11)
-the path curves downward
What is a TRAJECTORY?
-the path of a projectile through the air
A boat begins at point A and heads straight across a 60.0 meter wide river with a speed of 4 m/s (relative to the water). The river water flows north at a speed of 3 m/s (relative to the shore). The boat reaches the opposite shore at point C. What would cause the boat to reach the opposite shore in LESS time? (MOP-VP6)
-the river is 40 meters wide instead of 60 -the boat heads across the river at 5 m/s instead of 4 m/s
Vectors A, B and C are being added using the head-to-tail method in order to determine the resultant. Vector A is added first, then B, then C. If the vectors were added in a different order, then the resultant would have...? (MOP-VP2)
-the same magnitude and direction
What is the TAIL OF A VECTOR?
-the starting point of a vector (the end opposite the arrow head)
A stone is thrown horizontally from the top of a tower at the same instant a ball is dropped vertically. Which object is traveling faster when it hits the level ground below? (EBACKPACK QUIZ)
-the stone is traveling faster
What is the RESULTANT VECTOR?
-the vector sum of 2 or more vectors
What is RELATIVE VELOCITY?
-the velocity of an object as observed from a particular reference frame
Is "the free-fall acceleration" vector or scalar? (QUIZ QUESTION)
-vector
For 2-D motion, what is A(x) equal to?
0 m/s^2 -always assume X acceleration equals ZERO
A 5 ton airplane flies at 240 km/hr. If it experiences a 80 km/hr HEADWIND (coming straight on), what would the resultant velocity be?
160 km/hr
If a 5 ton airplane normally flies at 200 km/hr, but experiences a 50 km/hr tailwind (a wind coming from behind), what would the resultant velocity be? (MOP question)
250 km/hr
For 2-D motion, what is A(y) equal to?
9.8 m/s^2 -always assume Y acceleration equals 9.8
A plane flying horizontally at a speed of 50.0 m/s and at an elevation of 160 m drops a package. Two seconds later it drops a second package. How far apart will the two packages land on the ground? (EBACKPACK QUIZ)
=100 meters apart
A boat begins at point A and heads straight across a 60.0 meter-wide river with a speed of 3.0 m/s (relative to the water). The river water flows north at a speed of 4.0 m/s (relative to the shore). The boat reaches the opposite shore at point C. It will take the boat a time of approximately ______ seconds to travel across the river from point A to point C. HOW MANY SECONDS? (MOP-VP6)
=20 seconds
A small bug is flying straight downward at 5 m/s. Unknown to the bug, directly above him there is a diving bird also flying straight downward, but at 8 m/s. As seen by the bird, what is the velocity of the bug? (QUEST #10)
=3 m/s UPWARD
An Olympic athlete throws a javelin at 4 different angles above the horizontal, each with the same speed: 30 degrees, 40 degrees, 60 degrees, and 80 degrees. Which two throws cause the javelin to land the same distance away? (EBACKPACK QUIZ)
=40 degrees and 60 degrees
While running at 7 mph directly toward Patrick, Lisa passes a basketball to him. Patrick is stationary when he receives the ball, which is moving at a speed of 47 mph. How fast did Lisa throw the ball? (QUEST #10)
=40 mph
At what angle should a water-gun be aimed in order for the water to land with the greatest horizontal range? (EBACKPACK QUIZ)
=45 degrees
Two vectors, of magnitudes 25 and 70 are added. Which one of the following is a possible magnitude of the resultant?: 20, 40, 60, 100 (QUIZ QUESTION)
=60
For the winter, a duck flies 10.0 m/s due south against a gust of wind with a speed of 2.5 m/s. What is the resultant velocity of the duck? (EBACKPACK QUIZ)
=7.5 m/s south
A ball is thrown at an original speed of 8.0 m/s at an angle of 35 degrees above the horizontal. What is the speed of the ball when it returns to the same horizontal level? (EBACKPACK QUIZ)
=8.0 m/s
A person tosses a ball from the ground up into the air at an initial speed of 10 m/s and an initial angle of 43 degrees off the ground. After the ball is released, what is the total acceleration vector acting on the ball when the ball is at the top of its arc? (QUEST #11)
=9.8 m/s^2, DOWN
What is a PROJECTILE?
An object that travels through the air and experiences only acceleration due to gravity
What is the Pythagorean theorem?
C^2=a^2+b^2
TRUE OR FALSE: The river current effects the time it takes to cross to the opposite shore?
FALSE! River current does NOT effect time of the boat crossing!!
2 vectors with a magnitude of 5 units and 8 units are being added. The resultant vector could have a magnitude that ranges from _____ units to _____ units. (MOP question)
From 3 to 13 units
The vector sum of 2 or more vectors is known as the what? (MOP question)
Resultant
What are the trig identities?
SOH-CAH-TOA
If the x-component of B equals the magnitude of B, then... (QUIZ QUESTION)
Then...B(y)=0
What's the standard way to set up and equation so the variables are matching?
V(tw)=V(ts)+V(sw) -look at where the same letters match up