physics test # 2
A hockey puck slides off the edge of a horizontal platform with an initial velocity of 20.0 m/s horizontally and experiences no significant air resistance. The height of the platform above the ground is 2.0 m. What is the magnitude of the vertical component of the velocity of the puck just before it hits the ground?
-6.26 m/s
A ball is thrown horizontally with an initial velocity of 20.0 meters per second from the top of a tower 60.0 meters high. What is the initial vertical velocity of the ball?
0 m/s
If Earth had twice its present mass but it orbited at the same distance from the sun as it does now, its orbital period would be
1 year.
Which of the following vector diagrams represents the resultant of the following three vectors?
(see image)
The diagram above shows the resultant vector, R. Which diagram best represents a pair of component vectors, A and B, that would combine to form the resultant vector, R?
(see picture)
A boat, whose speed in still water is 8.0 m/s, crosses a river with a current of 6.0 m/s. If the boat heads perpendicular to the current, what is the speed of the boat relative to an observer standing on the shore as it crosses the river?
10. m/s
A motorboat is driven across a river at 3.00 km/hr at right angles to a current that is flowing at 10.0 km/hr. What is the resulting speed of the motorboat?
10.4 km/hr
A plane flying horizontally at a speed of 50 m/s and at an elevation of 160 m drops a package, and 2.0 s later it drops a second package. How far apart will the two packages land on the ground if air resistance is negligible?
100 m
Calculate the resultant vector for the diagram above. ^ (shows —> 10.0 m | 5.00 m)
11.2 M
Calculate the resultant vector for the diagram above.
11.2 meters
The reading on the spring scale is approximately
110 N
A plane has an airspeed of 142 m/s. A 30.0 m/s wind is blowing southward at the same time as the plane is flying. What must be the heading of the plane in order to move directly eastward relative to the ground?
12.2 degrees north of east
Mr. Smith drives his car a distance of 8.0 kilometers west. Then he turns and drives 12 kilometers north before again turning and driving 3.0 kilometers east to arrive home. If Mr. Smith had instead driven in a straight line from his starting point to his home, how many kilometers would he have driven?
13 km
What is the magnitude of side A?
13.4 m
A plane has an airspeed of 142 m/s. A 56.0 m/s wind is blowing southward at the same time as the plane is flying. If the velocity of the plane relative to the ground is directly eastward, what is the magnitude of that velocity?
131 m/s
A 60.0 kilogram car travels clockwise in a horizontal circle of radius 10.0 meters at 5.0 meters per second. The magnitude of the centripetal force acting on the car is
150 N
Two cars are approaching an intersection. Car A is 100.0 meters from the intersection and travelling south at a speed of 10.0 m/s. Car B is 200.0 meters intersection and travelling west at a speed of 15.0 m/s. How far apart are the cars (in terms of displacement) after 4.0 seconds?
152 meters
A plane has an eastward heading with an airspeed of 156 m/s. A 20.0 m/s wind is blowing southward at the same time as the plane is flying. The velocity of the plane relative to the ground is
157 m/s at an angle 7.31° east of south.
A wind farm generator uses a two-bladed propeller mounted on a pylon at a height of 20.0 m, as shown in the figure. The width of the pylon is very narrow, and the length of each propeller blade is 12.0 m. A tip of the propeller breaks off just when the propeller is vertical. The fragment flies off horizontally, falls, and strikes the ground at point P with negligible air resistance. Just before the fragment broke off, the propeller was turning uniformly, taking 1.20 s for each rotation. Approximately how far is point P from the base of the pylon?
160 m
A 4.0 kg rock and 1 kg stone fall freely from rest from a height of 100 meters. After they fall for 2.0 seconds, the ratio of the rock's speed to the stone's speed is
1:1
An object moves in uniform circular motion, and the centripetal force on the object is 4.0 N. If the mass of the object decreases by a factor of 2, what will be the centripetal force on the object?
2 N
A hiker walks 3.00 km north, 4.00 km east, 5.00 km south, and 4.00 km west. The magnitude of the resultant displacement of the hiker is
2.00 km south
An airplane flies 110.0 km East, then 235 km South. What is the magnitude (in km) of the airplane's net displacement?
259 km SE
A 0.50 kg toy is attached to the end of a 1.0 m very light string. The toy is whirled in a horizontal circular path on a frictionless tabletop. If the maximum tension that the string can withstand without breaking is 350 N, what is the maximum speed the mass can have without breaking the string?
26 m/s
You throw a rock horizontally off a cliff with a speed of 20.0 m/s and no significant air resistance. After 2.0 s, the magnitude of the velocity of the rock is closest to
28 m/s
One way that future space stations may create artificial gravity is by rotating the station. Consider a donut shaped space station 380.0 m in diameter that is rotating about its longitudinal axis. Astronauts walk on the inside surface of the ring-shaped space station. Approximately how long should it take for each rotation of the cylinder if it is to provide "normal" gravity for the astronauts?
28 s
You throw a rock horizontally off a cliff with a speed of 20.0 m/s and no significant air resistance. After 2.0 s, the magnitude of the velocity of the rock is closest to
28.0 m/s
A ball rolls over the edge of a platform with only a horizontal velocity. The height of the platform is 1.6 m and the horizontal range of the ball from the base of the platform is 20.0 m. What is the horizontal velocity of the ball just before it touches the ground? Neglect air resistance.
35 m/s
A person walks 10.0 km due east, then 30.0 km at 60.0° N of E. What is the shortest route back to his starting point?
36 km at 46° S of W
A person throws a ball horizontally from the top of a building that is 24.0 m above the ground level. The ball lands 100.0 m down range from the base of the building. What was the initial velocity of the ball? Neglect air resistance.
45.2 m/s
Centripetal force Fc acts on a car going around a curve. If the speed of the car were twice as great, the magnitude of the centripetal force necessary to keep the car moving in the same path would be?
4fc
A stone is thrown horizontally with an initial speed of 10.0 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.30 s. What is the approximate height of the cliff if air resistance is negligibly small?
91 m
Shown above are several trajectories followed by a ball. Assuming that air resistance is negligible, which ball stayed in the air the longest?
A
James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. Compare the time it takes each to reach the lake below if there is no air resistance.
James and John will reach the surface of the lake at the same time.
Which of the following would not be an example of a force acting centripetally?
The normal force of a table pushing up on a spinning ball.
The gravitational field of the planet Earth
has a strength of 9.80 newtons per kilogram
For projectile motion with no air resistance, which of the following remains constant?
horizontal component of velocity, vx
"Hang time" is the time a jumper's feet are off the ground in a vertical jump. If a person jumped straight up and measured his/her hang time, then runs horizontally and jumps with the same vertical component of takeoff velocity, the hang time will be
no different
If the earth were four times as far from the sun as it is now, the gravitational force between it and the sun would be
one-sixteenth as strong
The path of a projectile fired at a 30 degree angle to the horizontal is best described as
parabolic
A car goes around a circular curve on a horizontal road at constant speed. What is the direction of the friction force on the car due to the road?
perpendicular to the curve inward.
In the equation Fg = G(m1m2) / r2, the letter G is
the Universal Gravitational Constant
When a car goes around a circular curve on a horizontal road at constant speed, what force causes it to follow the circular path? the friction force from the road.
the friction force from the road.
An airplane with an airspeed of 120.0 km/h has a heading of 30.0° east of north in a wind that is blowing toward the west at 30.0 km/h. What is the approximate speed of the plane relative to the ground?
110 km/hr
In an air-free chamber (vacuum), a pebble is thrown horizontally, and at the same instant a second pebble is dropped from the same height. Compare the times of fall of the two pebbles.
They hit at the same time.
You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the friction between the tires and the road to become zero. While the car is on the ice, it
moves along a straight-line path away from the center of the circle.
The early models of the solar system were wrong because
they were based on the assumption that the earth was the center of the solar system
At the instant shown in the diagram, the car's centripetal acceleration is directed
toward E
If the circular track were to suddenly become frictionless at the instant shown in the diagram, the car's direction of travel would be
toward N
If the Earth were twice as massive as it is now, the gravitational force between it and the sun would be
twice as strong
Which graph best represents the magnitude of the centripetal force of the car above as a function of time?
(see picture)
Which graph best represents the relationship between the magnitude of the centripetal acceleration and the speed of an object moving in a circle of constant radius?
(veiw picture)
A rock is tied to a string and swung in a clockwise, vertical circle. When the rock is at the position shown, which of the following indicates the direction of vt (tangential velocity), ac (centripetal acceleration), and/or Fg (weight)?
(see picture)
A steel ball is attached to a string and is swung in a circular path in a horizontal plane. At point P, the string suddenly breaks near the ball. If these events are observed from directly above, which of the paths would the ball most closely follow after the string breaks?
(see picture)
Shown below are the velocity and acceleration vectors for an object in several different types of motion. In which case is the object slowing down and turning to its right?
(see picture)
A 1.00•10^3 kilogram car is driven clockwise around a flat circular track of radius 25.0 meters. The speed of the car is a constant 5.00 meters per second. What minimum friction force must exist between the tires and the road to prevent the car from skidding as it rounds the curve?
1.00•10^3 N
Mary and Debra stand on a snow-covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30° below the horizontal; Debra throws her snowball upward, at 30° above the horizontal. Which of the following statements are true about just as the snowballs reach the ground below?
Both snowballs will hit the ground with the same speed.
A rock is thrown from the upper edge of a tall cliff at some angle above the horizontal. It reaches its highest point and starts falling down. Which of the following statements about the rock's motion are true just before it hits the ground?
Its horizontal velocity component is the same as it was just as it was launched.
A spaceship is traveling to the Moon. At what point is it beyond the pull of Earth's gravity?
It is never beyond the pull of Earth's gravity.
The diagram shows a student seated on a rotating circular platform, holding a 2.0 kilogram block with a spring scale. The block is 1.2 meters from the center of the platform. The block has a constant speed of 8.0 meters per second. [Frictional forces on the block are negligible.] Which statement best describes the block's movement as the platform rotates?
Its velocity is directed tangent to the circular path, with an inward acceleration.
Let the orbital radius of a planet be R and let the orbital period of the planet be T. What quantity is constant for all planets orbiting the sun, assuming circular orbits?
T2/R3
Which of the following statements are true about an object in two-dimensional projectile motion with no air resistance?
The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.
You are driving a car, and unwisely place a cup of coffee on your dash board. When making a sharp left turn, from your frame of reference (an accelerated one) it appears that as you turn left your coffee cup accelerates to your right across the dash board and upon impact with the passenger side of the car spills all over your passenger door. An observer in a stationary hovering helicopter from above in an inertial (or un-accelerated) frame of reference would notice the coffee cup
moves in a straight line (does not accelerate)
For general projectile motion with no air resistance, the vertical component of a projectile's acceleration
remains a non-zero constant
A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped vertically. Which object is traveling faster when it hits the level ground below if neither of them experiences any air resistance?
the ball
Which factor, when doubled, would produce the greatest change in the centripetal force acting on the car?
velocity of the car
Newton had the insight to see that the -
force pulling on the moon has the same nature as the weight of an object sitting on the surface of the earth
Which represents the greatest centripetal acceleration?
(see picture)
A swimmer heading directly across a river that is 200.0 m wide reaches the opposite bank in 6 min 40 s. During this swim, she is swept downstream 480 m. How fast can she swim in still water?
0.50 m/s
A projectile was launched horizontally with a velocity of 468 m/s, 1.86 m above the ground. How long did it take the projectile to hit the ground?
0.616 s
A displacement vector is 34.0 m in length and is directed 60.0° west of north. What are the components of this vector?
17.0 m Northward, 29.4 m Westward
A boat moves 2.50 m/s north across a river flowing 1.20 m/s east. What is the approximate speed of the boat relative to the shore?
2.8 m/s
What approximate speed can a 1000.0 kg car travel around a horizontal unbanked curve whose radius is 0.20 km if the tires are capable of exerting a maximum frictional force of 4500 N?
20 m/s
A hockey puck slides off the edge of a platform with an initial velocity of 20.0 m/s horizontally. The height of the platform above the ground is 2.0 m. What is the approximate magnitude of the velocity of the puck just before it touches the grouWhen a car goes around a circular curve on a horizontal road at constant speed, what force causes it to follow the circular path? the friction force from the road. nd? You can neglect air resistance.
21 m/s
A hockey puck slides off the edge of a platform with an initial velocity of 20.0 m/s horizontally. The height of the platform above the ground is 2.0 m. What is the approximate magnitude of the velocity of the puck just before it touches the ground? You can neglect air resistance.
21 m/s
A player throws a football 50.0 m at 61.0° north of west. What is the westward component of the displacement of the football?
24.2 m
A car travels 20.0 km west and then 20.0 km south. What is the magnitude of its displacement vector?
28.3 km
Ball II has twice the mass of Ball I, and both are moving in circles of equal radii at the same speed. How do the net forces of Ball I and Ball II compare?
2F1 = F2
Mithra is an unknown planet that has two moons, A and B, in circular orbits around it. The table summarizes the hypothetical data about these moons. What is the approximate mass of Mithra?
3.0•10^23 kg
As shown in the diagram above, a student standing on the roof of a 50.0 meter high building kicks a stone at a horizontal speed of 4.00 m/s. How much time is required for the stone to reach the level ground below? (Neglect Air Resistance.)
3.19 seconds
Neglecting air resistance, if a ball is thrown at 4.5 m/s horizontally from a 94 m high cliff, how far has the ball fallen after 2.7 s?
36 m
What is the resultant of a 3.00 meter vector and 4.00 meter vector at right angles to each other?
5.00 m
A 5.23 meter ladder leans against a wall (at a 29.4° angle of elevation). What is the height above the ground where the top of the ladder makes contact with the wall?
5.23 meters • sin (29.4°)
The curved section of a horizontal highway is a circular unbanked arc of radius 740 m. If the coefficient of static friction between this roadway and typical tires is 0.40, what would be the maximum safe driving speed for this horizontal curved section of highway?
54 m/s
You walk 53.0 m to the north, then you turn 60.0° to your right and walk another 45.0 m. Determine the approximate direction of your displacement vector. Express your answer as an angle relative to east.
63° N of E
You walk 33.0 m to the north, then turn 60.0° to your right and walk another 45.0 m. Approximately how far are you from where you originally started?
68 m
An airplane undergoes the following displacements, all at the same altitude: First, it flies 59.0 km in a direction 30.0° east of north. Next, it flies 58.0 km due south. Finally, it flies 100.0 km 30.0° north of west. Use components to determine how far the airplane ends up from its starting point.
71.5 km
A cannon with a barrel velocity of 140 m/s launches a cannonball horizontally from a tower. Neglecting air resistance, what vertical distance will the cannonball have fallen after 4.00 seconds?
78.5 m
Marvin the Martian (mass = 35.0 kg) has a weight of 280.0 Newtons on the surface of Planet X. What is the acceleration due to gravity on Planet X?
8.00 m/s^2
An object travels around a 120 m radius circular path at a constant 70.0 m/s. The centripetal force on the object is 35,000 N. What is the mass of the object?
860 kg
A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will
be directly over the package
In order to calculate the force of attraction (Fg) between the Earth and the Sun using Newton's Law of Universal Gravitation, one must know the distance
between the center of the Sun to the center of the Earth.
The diagram above represents a mass, m, being swung clockwise at a constant speed in a horizontal circle. At the instant shown, the centripetal force acting on mass m is directed towards
c
A car moves with a constant speed in a clockwise direction around a circular path of radius r, as represented in the diagram above. When the car is in the position shown, its acceleration is directed toward the
east
Earth's path around the sun brings it closer to the sun during some parts of the year and further away at other times. According to Kepler's Laws of Planetary Motion, Earth's speed is
faster at times when it is closer to the sun.
Which of the following is NOT one of Kepler's Laws of Planetary Motion?
for every action there is an equal and opposite reaction
You are trying to cross a river that flows toward the 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 general northwesterly direction.
Halley's Comet is in a highly elliptical orbit around the sun. Therefore the orbital speed of Halley's Comet, while traveling around the sun,
increases as it nears the sun
When an object moves in uniform circular motion, the direction of its acceleration is
is directed toward the center of its circular path.
A projectile is fired horizontally in a vacuum. The projectile maintains its horizontal component of speed because it
is not acted on by any horizontal forces
A child is riding on a merry-go-round. As the speed of the merry-go-round is doubled, the magnitude of the centripetal force acting the child is
is quadrupled
The Law of Universal Gravitation was first proposed by
isaac newton
The mathematical description of planetary motion was first described by
johannes kepler
James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. If there is no air resistance, when they reach the lake below
the splashdown speed of John is larger than that of James.
How would you represent the horizontal component, vx, of the velocity vector shown in the diagram above?
vx = 10m/s • cos(45°)
The x and y components of a displacement vector are 1.23 m and 8.90 m respectively. What angle does the vector make with the x axis?
θ = 82.1°
