# Physics Chapter 7: Projectile Motion

c
A vector is a quantity that has
a. magnitude and time
b. time and direction
C. magnitude and direction
b
A scalar is a quantity that has
a. direction
b. magnitude
c. time
d. color
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d
When representing velocity as a vector,
a. the direction of the arrow shows the direction of motion
b. the length of the arrow represents the speed
c. the length of the arrow is drawn to a suitable scale
d. all of the above
e. none of the above
c
In order to find the components of a vector, you should
a. draw the vector with correct magnitude and orientation
b. measure the sides of the rectangle
c. draw a rectangle so that the vector is diagonal
d. all of the above
b
Which of the following would NOT be considered a projectile?
a. a cannonball thrown straight up
b. a cannonball rolling down a slope
c. a cannonball rolling of the edge of a table
d. a cannonball thrown though the air
e. all of the above are projectiles
c
The horizontal component of a projectile’s velocity is independent of
a. the range of the projectile
b. time
c. the vertical component of its velocity
a
In the absence of air friction, the vertical component of a projectile’s velocity doesn’t change as the projectile moves
a. always false
b. always true
c. sometimes true
c
In the absence of air friction, the horizontal component of a projectile’s velocity doesn’t change as the projectile moves
a. sometimes true
b. always true
c. always false
a
At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?
a. neither. They both hit the ground at the same time
b. the dropped ball
c. the horizontally thrown ball
d
A ball is thrown into the air at some angle. At the very top of the ball’s path, its velocity is
a. entirely vertical
b. there’s not enough information given to determine
c. both horizontal and vertical
d. entirely horizontal
c
In the absence of air resistance, the angle at which a thrown ball will go the farthest is
a) 15 degrees
b) 30 degrees
c) 45 degrees
d) 60 degrees
e) 75 degrees
c
At what part of a path does a projectile have minimum speed?
a) when it returns to the ground
b) halfway to the top
c) at the top of it’s path
d) when it is thrown
e) there’s not enough information to say
c
A cannonball is launched from the ground at an angle of 30 degrees above the horizontal and a speed of 30 m/s. Ideally (no air resistance) the ball will land on the ground with a speed of
a) 0 m/s
b) 20 m/s
c) 30 m/s
d) 40 m/s
e) there’s not enough information to say
d
A projectile is fired horizontally in a vacuum. The projectile maintains its horizontal component of speed because
a) has no vertical component of speed to begin with
b) is not acted on by any forces
c) the net force acting on it is zero
d) is not acted on by any horizontal forces
e) none of the above
c
A cannonball is launched horizontally from a tower. If the cannonball has a barrel velocity of 60 m/s, where will the cannonball be 1 second later? (neglect air resistance)
a) 6 m downrange
b) 30 m downrange
c) 60 m downrange
d) 300 m downrange
e) none of the above
c
After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, it acceleration is (neglecting air resistance)
a) les than when it was at the top of its path] b) greater than when it was at the top of its path
c) the same as when it was at the top of it’s path
a
An airplane flying into the head wind loses ground speed, and an airplane flying with he win gains ground speed. If an airplane flies at right angles to the wind, the ground speed is
a) more
b) unchanged
c) less
c
Which best approximates the resultant of a pair of 6-unit vectors at right angles to each other?
a) 0 units
b) 6 units
c) 8 units
d) 12 units
b
What is the resultant of a 3-unit vector and a 4-unit vector at right angles to each other?
a) 1 unit
b) 5 units
c) 7 units
d) none of the above
e
Suppose a small plane can fly at 170 km/h relative to the surrounding air. Suppose also that there is a 60 km/h tail wind. How fast does the plane’s shadow move across the ground?
a) 5 km/h
b) 60 km/h
c) 110 km/h
d) 170 km/h
e) 230 km/h
a
At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?
a) Neither-the both hit the ground at the same time
b) the horizontally thrown ball
c) the dropped ball
c
A ball is thrown straight upward at 10 m/s. Ideally (no air resistance), the ball will return to the thrower’s hand with a speed of
a) 0 m/s
b) 5 m/s
c) 10 m/s
d) 20 m/s
e) there is not enough information to say
a
A cannonball with a barrel velocity of 140 m/s launches a cannonball horizontally from a tower. Neglecting air resistance, how far vertically will the cannonball have fallen after 4 seconds?
a) 80 m
b) 140 m
c) 560 m
d) 2240 m
e) none of the above
F
T/F: A quantity that has both magnitude and direction is called a scalar
F
T/F: A quantity that has only magnitude is called a vector
T
T/F: The vector sum is called the resultant
T
T/F: The length of a vector represents its magnitude
F
T/F: A single vector can be replaced by two vectors in the x- and y- directions that are right angles to each other. The two x and y vectors are called the resultant of the original vector
F
T/F: A ball will go the farthest is thrown almost horizontally
T
T/F: Wind velocity can be represented as a vector quantity
Gravity x time
Vertical Velocity
Distance/time
Horizontal Velocity
Velocity x time
Horizontal Distance
5t^2
Vertical Distance
Square root of distance/5
Time
a^2 + b^2 = c^2
Pythagorean Theorem
Tangential velocity
Why does the moon continuously fall around the earth instead of into it?
Satellite
A projectile moving fast enough to fall continuously around the earth.
5 m/s
Harry jumps horizontally from the top of a building that is 20.0 m high, hopes to reach a swimming pool that is at the bottom of the building, 10.0m horizontally from the edge of the building. If he is to reach the pool, what must his jumping speed be?

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