Vector Questions
Which angle gives max range? Air time?
45, 90 -launch angles that are complementary all equal the same range
Two vectors, of magnitudes 25 and 70, are added. Which one of the following is a possible magnitude of the resultant? A. 20 B. 40 C. 60 D. 100
60
A ball is thrown at an original speed of 8.0 m/s at an angle of 35° above the horizontal. What is the speed of the ball when it returns to the same horizontal level?
8.0 m/s
What is distance?
A scalar quantity that refers to how much ground an object has covered during its motion and must account for the entire path traveled
What is acceleration?
A vector quantity that is defined as the rate at which an object changes its velocity -NOT how fast, it is about CHANGING how fast -an object is accelerating if the velocity is changing -speeding up, slowing down, changing direction
What is displacement?
A vector quantity that refers to how far out of place an object is and the overall change in position -only care about starting and ending position- path does not matter (the straight line distance between where you were and where you ended up)
In a school playground, a child runs 5 m in the positive (+) x-direction and then 2.0 m in the negative (-) y-direction. Which of the following expressions represents the magnitude of the child's resultant displacement?
Square root (5m)^2 + (-2)^2
What does a triangle stand for?
Stands for Chang's (delta) -displacement is Xf-Xi Xt2-Xt1
What is free fall?
State of movement that results from gravitational force only (no air resistance or friction) -in absence of air resistance, all objects will fall vertically with the same constant acceleration (9.8m/s/s)
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
Straight down
What is relative velocity?
The velocity of an object as observed from a particular reference frame
What is average speed?
The average speed of all the instantaneous speeds and is found by a distance time ratio -if an object travels at a constant speed, the instantaneous speed at any point is the same as the average speed
Suppose that an object travels from one point in space to another. Make a comparison between the displacement and the distance traveled
The displacement is either less than or equal to the distance traveled.
In a PT graph, when is the object moving in the positive direction?
The line is above the 0
On a PT graph, when is the object slowing down?
The line is curved and gets flatter
On a VT graph, when is the object's velocity changing?
The line is moving away from the X axis
On a VT graph, when is the object slowing down?
The line is moving toward the X axis
What is range?
The maximum horizontal distance the projectile can travel
What is projectile motion?
The motion of an object that is subject only to acceleration of gravity -no air resistance -acceleration is always 9.8 and directed downward
For any given motion, the velocity is
The rate at which the object's position changes
Which of the following would cause the boat to reach the opposite shore at a location SOUTH of C?
The river flows north at 2 m/s
Which of the following would cause the boat to reach the opposite shore in LESS time?
The river is 40 m wide
On a PT graph, when is the object at a constant velocity?
The slope is constant and there is a straight line
On a PT graph, when is the object moving in the negative direction?
The slope is negative or going downhill
What is instantaneous speed?
The speed at any given instant in time -like a speedometer reading
On a PT graph, when is the object's velocity changing?
There is a curved line with increasing slope
On a VT graph, when is the object at a constant velocity?
There is a horizontal line not on the zero
A bullet is fired horizontally, and at the same instant a second bullet is dropped from the same height. Ignore air resistance. Compare the times of fall of the two bullets.
They hit at the same time
What is velocity?
Vector quantity that represents the rate at which an object changes it's position -speed with a direction
A scalar is a quantity that is fully described by
magnitude alone
Velocity is an example of a vector quantity because it has
magnitude and direction
In a diagram, the length of a vector arrow represents the
magnitude of the vector
A passenger on a bus moving east sees a man standing on a curb. From the passenger's perspective (frame of reference), the man is
moving west at a speed that is equal to the bus's speed.
What are vectors?
quantities that have magnitude and direction
Which of the following is a physical quantity that has a magnitude but no direction?
scalar
Identify the following quantities as scalar or vector: the speed of a snail, the time it takes to run a mile, the free-fall acceleration.
scalar, scalar, vector
For any given motion, the distance is
the amount of ground which is covered by the moving object
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
in a northwesterly direction
Ignoring air resistance, the horizontal component of a projectile's acceleration A. is zero. B. remains a non-zero constant. C. continuously increases. D. continuously decreases.
is zero
The science of describing the motion of objects using words, diagrams, numbers, graphs, and equations
kinematics
What is a vector component?
-piece of a vector that points in either the vertical or horizontal direction -projections of the vector onto an axis -describes the effect of a vector in a given direction -each can be expressed as the sum of its horizontal and vertical components
The boat reaches the opposite shore at point C. Point C is approximately ___ feet north of point B.
45
What is the rule of thumb for an object traveling in a straight line?
-speeding up-the acceleration is same direction -slowing down- the acceleration is in the opposite direction -if velocity is positive, acceleration is positive -if velocity is negative and the object is slowing down, the acceleration is positive
If two objects have the same peak, which is in the air longer? which has a smaller initial velocity?
-they will be in air for same time, the smaller distance or the larger angle
If vectors X and Y are added, then the resultant would be best represented by vector
/ x and \y = D
What are the four points in counterclockwise convention?
0, 90, 180, 270 -the arrow is proportional to the magnitude
A physics teacher moves once around the perimeter of a rectangular table with the dimensions 1m by 2m. What is the overall displacement?
0m
A ball is thrown with a velocity of 20 m/s at an angle of 60° above the horizontal. What is the horizontal component of its velocity at the exact top of its trajectory?
10 m/s
You are traveling at 55 mi/h in the +x axis relative to a straight, level road and pass a car traveling at 45 mi/h. The relative velocity of your car to the other car is
10 mi/h
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?
100 m
It will take the boat a time of approximately ___ seconds to travel across the river from point A to point C.
15
How many displacement vectors shown in the figure above have a horizontal component pointed in the -x direction?
2 on the left of the graph
tile is launched horizontally with a velocity of 30 m/s. After 4 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. List the letters of the two answers in their respective order (horizontal first, then vertical). A. 0 B. 10 C. 20 D. 30 E. 40 F. 50 G. 60 H. 70
30, 40
A projectile is launched upward at an angle to the horizontal. The initial horizontal velocity is 40 m/s; the initial vertical velocity is 30 m/s. After 4 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. List the letters of the two answers in their respective order (horizontal first, then vertical).
40, 10
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 at point C. If the river current was 4 m/s, then the boat would land on the opposite shore at ___. (Assume that the boat speed relative to the water does not change.)
A location north of C
What is the path of a projectile (in the absence of friction)?
A parabola
What does g represent in the range equation?
Absolute value of Ay
What is deceleration?
Acceleration in the direction opposite to velocity OR acceleration that results in a decrease in speed -does not mean negative acceleration
What is vector addition?
Add the vectors with head of 1st ends and second begins -head is arrow part -tail is line
In a PT graph, when is the object not moving?
Any horizontal line
On a VT graph, when is the object moving in the negative direction?
Any line below the X axis
What is a projectile?
Any object acted upon only by the force of gravity
In a VT graph, then is the object moving in the positive direction?
Anything above x axis
Which of the following vector addition sequences will result in a displacement equal to d1 + d2 + d3 A. d3 +d4 +d1 C. d2 +d4 +d3 B. d2+d1+d3 D. d4+d3+d1
B
A pilot wishes to fly from airport A to airport B. Airport B is located due west from airport A. The pilot's aircraft averages a speed of 160 mi/hr. If the pilot is flying in a wind that blows out of the north at a speed of 40 mi/hr, then the pilot should head his plane in the direction of vector
B \ but down more
Vector components are important in physics because they describe the
Effect of a vector in a given direction
What in a car changes the velocity?
Break pedal, steering wheel, gas pedal
If the x-component of B equals the magnitude of B, then
By equals zero
The magnitude of the vertical velocity of a projectile is ALWAYS ____. A. Zero B. 9.8 m/s C. constant D. changing E. increasing
Changing
In a coordinate system, a vector is oriented at angle θ with respect to the x-axis. The x component of the vector equals the vector's magnitude multiplied by which trigonometric function?
Cos 0
The Greek letter delta indicates a
Difference or change
Which of the following quantities is a vector? Mass Time Distance Displacement Temperature
Displacement
What are examples of scalars?
Distance, speed, mass, temperature, time
How to calculate average speed? Average velocity?
Distance/time =speed Average velocity: change in position/time
vectors are moved according to the rules of the head-to-tail method of vector addition, then the resultant vector is drawn
From the tail of the first to the head of the last
If two objects have a different peak, which is in the air longer?
Higher peak is in the air longer
What is magnitude?
How much or how many (no sign)
Suppose you are given a position v time graph. The slope of a lie drawn tangent to a point on the graph describes what quantity?
Instantaneous velocity
A northeast and a southeast vector are being added using the head-to-tail method. Which diagram below illustrates the correct method of adding two such vectors?
Look at ws (B)
What are acceleration units?
M/s/s Km/h/s Mi/h/s
Is it possible for velocity to be constant and still have acceleration?
No, velocity has no change in speed and cannot change direction
What is a frame of reference?
Perspective from which changes in position are being measured
Ignoring air resistance, the horizontal component of a projectile's velocity A. is zero. B. remains constant. C. continuously increases. D. continuously decreases.
Remains constant
The vector sum of two or more vectors is known as the
Resultant
What is speed?
Scalar that refers to how fast an object is moving
In the triangle below, what does the angle equal?
Tan- (y/x
What represents direction in a position time graph?
The + or -
Which of the following statements is true of a projectile's acceleration? A. The acceleration is directed upward as the projectile rises toward its peak. B. The acceleration is decreasing as the projectile rises upward toward its peak. C. The acceleration is increasing as the projectile falls downward from its peak. D. The acceleration value is dependent upon the mass of the projectile. E. The acceleration is a constant value.
The acceleration is a constant value
What shows you to not just add all the vectors together?
The arrow above the letter
What is the slope of a distance-time graph?
velocity
In a VT graph, when is the object not moving?
When there is a horizontal line on the 0
The car rolls from +3 m to +5 m which statement is true?
Xi = +3
Is it possible for speed to be constant and still have acceleration?
Yes if changing direction
What is slope in a VT graph?
acceleration
What is average acceleration?
change in velocity over change in time
Which displacement vectors shown in the figure above have vertical components that are equal?
d1 and d3; same height, not length
What are some examples of vectors?
displacement, velocity, acceleration
What is trajectory?
the path of a projectile
What is the resultant?
the sum of 2 or more vectors -the order they are added doesn't matter because it will always be same magnitude and direction
What is the instantaneous velocity?
the velocity of an object in motion at a specific point in time -slope of a line tangent to a specific point on the PVT curve -find the slope of the line
