Week 4
In order to withstand such g-forces (which in an F-16 can be greater than 9 g's a number of coping mechanisms have been developed. See here: https://youtu.be/pUZwVmH07Y4 You can see a more extended discussion of the problems involved in high g maneuvers here (there are two videos in sequence): http://www.youtube.com/watch?v=UvLM_uzNJZU 1. Considering what you know about circular motion, why are high speed and tight turns so dangerous? 2. Before losing consciousness many pilots experience loss of color vision and later tunnel vision during a high speed and tight turn. Describe two ways a pilot could reduce his g-forces if she found herself in such a situation and justify them in terms of the form of the centripatel acceleration in terms of the velocity, v, and radius, r. (Essay Question, I answer with my own words for each one)
1. The direction of the circular motion in this scenario is not constant. This means that when the pilot is directing the plane into a harsher turn their head will become closer to the center of the turn, while their feet will be away from the turn making the blood flow more towards them. This can cause them to lose consciousness, as the blood flow to their head will not be level. 2. A pilot could reduce their g-forces in two ways, but first you need to know the equation that will help determine how to reduce g-force: a=((v^2)/r) The first way requires you to know the relationship between centripetal acceleration and velocity. As you can tell from the equation, the larger the velocity, the larger the acceleration. The smaller the velocity, the smaller the acceleration. Since you must decrease centripetal acceleration to reduce g-forces, you must decrease velocity in order to reduce g-forces as this reduces acceleration. The second way requires you to know the relationship between centripetal acceleration and the radius in this scenario. As you can determine through the equation, the faster you accelerate the smaller the radius of the turn becomes as it becomes more compact, the slower you accelerate the larger the radius, as the turn becomes wider. Thus this means that if you have a larger radius, you can reduce your g-forces by decreasing the acceleration. Overall, decrease velocity or increase radius to reduce g-forces.-Not sure if it is right
In the cat shot video, the woman pilot experiences 5g's of acceleration or 52 m/s2. If she weighs normally 120 pounds on land, what is her apparent weight during this extreme acceleration? Group of answer choicesshe is weightless.24 pounds.120 pounds600 pounds.
600 pounds.
You are riding a very fast Ferris Wheel so that you actually notice a variation in your apparent weight. Where is your apparent weight maximum? Group of answer choicesAt the topAt the bottomHalfway up, going downHalfway up, going up
At the bottom
You go through a loop in a roller coaster at constant speed. Where is your apparent weight a maximum? Group of answer choicesAt the topAt the bottomHalfway up, going downHalfway up, going up
At the bottom
Your apparent weight is equal to your weight Group of answer choicesIn an elevator accelerating upwards.In an elevator accelerating downwards.In an elevator in free fall.In an elevator not accelerating.
In an elevator not accelerating.
You are in your friend's car, speeding down the road. The light ahead turns red, and your friend slams on the brakes. You feel yourself pulled into your shoulder strap. Lucky you were wearing your seat belt, or you would have slammed into the windshield. During this episode, the net force on you was Group of answer choicesIn the forward direction.In the backward direction.In the upward direction.There is no force on you.
In the backward direction.
Most of us don't get to experience truly extreme accelerations. An exception are navy pilots who must take off and land on aircraft carriers. To see what it is like to takeoff from an aircraft carrier see here: https://youtu.be/YgcMP-PyfTg Here is a pilot's first shot: http://www.youtube.com/watch?v=fYHDy81QO2Y Pretty intense isn't it? 0 to 180 mph in 200 ft, corresponds to 0 to 80 m/s in 61 meters or approximately 5 g's of acceleration (52 m/s^2). During the shot the pilot feels herself pushed back into her seat with an enormous force. What direction is the NET force on her? Group of answer choicesIn the rear direction.In the up direction.In the forward direction.There is no way to tell.
In the forward direction.
You are in your friend's car, waiting at a red light. The light turns green, and your friend accelerates rapidly. You feel yourself sink into the cushioning on the back of your seat. There is a net force on you, Group of answer choicesIn the forward direction.In the backward direction.In the upward direction.There is no force on you.
In the forward direction.
When you punch this Bozo the clown toy it tips over but then comes back upright for more. This happens because: The toy is filled with helium No matter how you tilt him, his center of mass rises When you tilt him a lever flips a weight to keep him in balance. There are springs at his base.
No matter how you tilt him, his center of mass rises
Which of the following is lists the vehicles in order of increasing stability in a high-speed turn? Group of answer choicesSUV, car, motorcycleSUV, motorcycle, carmotorcycle, car, SUVmotorcycle, SUV, car
Suv, car, motorcycle
You are traveling in a subway along a straight, level track at constant velocity. If you close your eyes, you can't tell which way you're heading. Why not? Group of answer choicesYou are not accelerating, so there are no fictitious forces acting on you.The force of friction and the force of gravity act in different directions, so you cannot choose which force acts in the direction of your motion.The motor in the subway car causes you to accelerate, but you cannot distinguish between the force of friction from the seat and the contact force from the seat.
The motor in the subway car causes you to accelerate, but you cannot distinguish between the force of friction from the seat and the contact force from the seat.-NOT RIGHT PROB: The force of friction and the force of gravity act in different directions, so you cannot choose which force acts in the direction of your motion.
Someone donates a brand new satellite dish for the house. You install a Satellite dish on the house so they can get 150 channels. To align the satellite dish you point it to the south at a particular angle to the horizon. You look at the TV signal as you align it and find that even tiny angular adjustments will cause you to lose the signal. There is one particular point in the sky where the satellite dish can point and the TV reception is excellent during the day time or at night. The reason this is the case is: Group of answer choicesThere is a broadcast station which is located in the kuiper belt which beams transmissions exactly to your house.There is a broadcast station located at the equator which bounces signals off the troposphere which you receive. There is a geosynchronous satellite which is fixed over the equator at a particular point. The satellite dish is aimed toward that point. There is a series of geosynchronous satellites which constantly appear at that point in the sky, each one appearing for several hours before being replaced by another satellite
There is a geosynchronous satellite which is fixed over the equator at a particular point. The satellite dish is aimed toward that point.
During the trip you put a DVD on the player and snooze off in the back seat. You jerk awake and notice a book on the floor which is sliding over to the right. You surmise that the car is Group of answer choicesTurning right and the acceleration is to the rightTurning left and the acceleration is to the leftTurning right and the acceleration is to the leftTurning left and the acceleration is to the right.
Turning left and the acceleration is to the left
If you are riding a roller coaster and want to maximize your feelings of weightlessness during the ride over the hills, where is the best place to sit? Group of answer choicesin the last car (back)in the first car (front)in the front or backanywhere, you feel the same thing in every seat of the roller coaster
WRONG SOMEHOW: in the last car (back)
While waiting for a friend, you try to balance a ballpoint pen on its point. You occasionally get it to remain vertical and motionless for a second or so, but it inevitably falls over. When the pen is vertical and remains motionless for a second, it is Group of answer choicesnot in equilibrium, but rather at a point of maximum upward momentum.in a stable equilibrium with a minimum total potential energy.in an unstable equilibrium with a maximum total potential energy.not in equilibrium, but rather at a point of maximum total kinetic energy.
WRONG: not in equilibrium, but rather at a point of maximum upward momentum.
You are watching a motorbike race on television. You notice that the bikers lean on the direction of the turns when they are in a curve. Why do they do that? Group of answer choicesso that they can push the other bikers if they get too closeso that the net force is directed towards its center of massso that the torque on the bike is maximumso that the net torque on the bike is zero
WRONG: so that the net force is directed towards its center of mass
You are riding a multi-speed bicycle up a steep hill that's 100 m high and want to exert as little force as possible on your way up the hill. Group of answer choicesYour choice of gears doesn't matter because you'll exert the same amount of force climbing the hill no matter which gear you choose.You should choose the largest crank sprocket (attached to the pedals) and the smallest freewheel sprocket (attached to the rear wheel).You should choose the smallest crank sprocket (attached to the pedals) and the largest freewheel sprocket (attached to the rear wheel).You should choose the largest crank sprocket (attached to the pedals) and the largest freewheel sprocket (attached to the rear wheel).
You should choose the smallest crank sprocket (attached to the pedals) and the largest freewheel sprocket (attached to the rear wheel).
A bathroom scale reads Group of answer choicesYour weightYour apparent weightThe force with which the earth attracts youYour mass in kg
Your apparent weight
A ball is moving in a circular path at a constant speed. The ball has Group of answer choicesa non-zero net force.no net force.not enough information is given to determine the force.
a non-zero net force.
An astronaut orbiting the earth inside the space shuttle floats in air. He is Group of answer choicesnot acceleratingaccelerating directly towards the center of the earthaccelerating in the direction of the orbital motionasccelerating opposite the direction of the orbital motion
accelerating directly towards the center of the earth
You travel quickly around the loop-the-loop of a roller coaster and find that you can't even tell when you are upside-down without looking. At the very top of the loop, you are Group of answer choicesaccelerating upward.not accelerating. You are just coasting forward horizontally.accelerating downward less fast than the acceleration due to gravity.accelerating downward faster than the acceleration due to gravity.
accelerating downward faster than the acceleration due to gravity.
An object is in stable equilibrium when Group of answer choicesthe NET force is zero.the acceleration is zero.any small shift increases its total potential energy.the momentum is zero.
any small shift increases its total potential energy.
If there were no launch pad beneath the space shuttle at lift-off, the upward thrust of its engines would be: approximately zero. approximately half as much. approximately unchanged. approximately twice as much.
approximately unchanged.
You find a half-sunken barge which is full of compressed helium gas cylinders which you empty out. To have some fun, you get one of the full helium gas cylinders and put it on top of a dolly (a wheeled platform). You sit behind the gas cylinder and point the opening of the cylinder in the backward direction. When you open the valve on the gas cylinder the helium gas goes rushing out with a loud roar! The dolly accelerates rapidly in the forward direction. To see a similar (but MUCH more dangerous!) situation, look here: http://www.youtube.com/watch?v=ejEJGNLTo84Links to an external site. This happens because Group of answer choicesThe stream of helium gas hits a wall and pushes off it, forcing the dolly forwardThe mass of the cylinder becomes less, forcing the dolly in the forward directionas the mass of helium moves in the reverse direction, the dolly recoils in the forward direction. a vacuum forms near the nozzle. When the air rushes back in (nature abhors a vacuum) it pushes the dolly in the forward direction.
as the mass of helium moves in the reverse direction, the dolly recoils in the forward direction.
A bicycle automatically steers so as to return you to an unstable equilibrium. That unstable equilibrium occurs when your center of gravity is Group of answer choicesat its maximum possible height.behind the rear wheel.at its minimum possible height.in front of the front wheel.
at its maximum possible height.
As you ride an elevator, you sometimes feel heavier than normal. Two occasions when you feel more than your normal weight are Group of answer choicesat the start of a trip downward and at the start of a trip upward.at the end of a trip downward and at the start of a trip upward.at the start of a trip downward and at the end of a trip upward.at the end of a trip downward and at the end of a trip upward.
at the end of a trip downward and at the start of a trip upward.
As you ride an elevator, you sometimes feel lighter than normal. Two occasions when you feel less than your normal weight are Group of answer choicesat the start of a trip downward and at the start of a trip upward.at the end of a trip downward and at the start of a trip upward.at the start of a trip downward and at the end of a trip upward.at the end of a trip downward and at the end of a trip upward.
at the start of a trip downward and at the end of a trip upward.?
You go through a loop in a roller coaster at constant speed. Where is your apparent weight a minimum? Group of answer choicesAt the topAt the bottomHalfway up, going downHalfway up, going up
at the top
You have just opened a can with a can opener and the lid drops on the floor. This thin metal disk rolls for a surprising distance before falling over. The lid manages to remain upright so long because it Group of answer choiceshas so little gravitational potential energy.is in a stable equilibrium as it rolls.automatically steers itself back to its unstable equilibrium as it rolls.has so much total energy.
automatically steers itself back to its unstable equilibrium as it rolls.
The tumble dryer in the laundry room spins its drum about a horizontal axis. The clothes in this drum rise part way up the side of the drum as it turns and then fall back toward the bottom of the drum, over and over again. If the drum turned too fast, this tumbling effect wouldn't work because the
clothes' inertia would keep them pressed against the drum as it spun.
As you make a left turn on a bicycle, you tip the bicycle into the turn. You do this so that the two forces on the bicycle tires exert a combined force directed at your overall center of mass. Because it is directed at your center of mass, this combined force Group of answer choicesexerts no torque on your and the bicycle about your center of mass.does not make you and the bicycle accelerate.points in exactly the opposite direction as your weight.is exactly zero.
exerts no torque on your and the bicycle about your center of mass.
When you make a left turn on a bicycle, the force that causes you to accelerate to the left is applied by Group of answer choicesfriction between the ground and the wheels.your right hand on the handle bar.your left hand on the handle bar.either or both hands on the handle bar.
friction between the ground and the wheels.
If a bicycle wheel is rolling and starts to fall over to the left, it will turn to the left.This is an example of Group of answer choicescentripetal accelerationelastic restoring forcedynamic instabilitygyroscopic precession
gyroscopic precession
It is difficult to balance a quarter along its edge because if it begins to tilt it immediately falls to the ground. However if you roll the quarter along the floor it can remain upright for remarkably long periods of time. In particular, you notice that if it begins to tilt, instead of falling down immediately, the quarter begins to turn in the direction of the tilt, and frequently restabilizes itself. The reason this happens is because of Group of answer choicesmagic.gyroscopic precession.the rolling coin creates its own magnetic field.the coins linear momentum.
gyroscopic precession.
While an astronaut is making a spacewalk near the Space Shuttle, Group of answer choiceshe has zero weight and therefore feels weightless.he has only a microgravity weight, so he feels almost weightless.he has a large weight, but feels weightless because he is falling.he has a large weight, but he is not accelerating so he feels weightless.Titla: Circular
he has a large weight, but feels weightless because he is falling.
The curves on bicycle racetracks are steeply banked, so that the inner edge of each curve is much lower than its outer edge. This banking tips the support force that the track exerts on the bicycle wheel toward the center of each turn. That center-directed or centripetal force on the bicycle is important because it Group of answer choiceshelps the bicycle accelerate inward to complete each turn without skidding.it does work on the bicycle during each turn and thus increases the bicycle's energy.balances the outward centrifugal force that the bicycle experiences as it completes each turn, so that the bicycle experiences zero net force.it does negative work on the bicycle during each turn and thus decreases the bicycle's energy.
helps the bicycle accelerate inward to complete each turn without skidding.
Skateboarders often can skate on the inner surface of cylindrical or bowl - shaped tracks. As a result, the normal (support) force is able to point inwards towards the center of the circle wherever the person is. That center-directed or centripetal force on the skate wheels is important because it Group of answer choiceshelps the skater accelerate inward to complete each turn without skidding.it does work on the skater during each turn and thus increases the skater's energy.balances the outward centrifugal force that the skater experiences as it completes each turn, so that the skater experiences zero net force.it does negative work on the skater during each turn and thus decreases the bicycle's energy.
helps the skater accelerate inward to complete each turn without skidding.
The spacecraft used in most science fiction movies never seem to require refueling. Presumably, they have great energy reserves located on-board somewhere. But rockets can't operate on energy alone because Group of answer choicesthey propel themselves forward by pushing stored mass backward as exhaust.rockets are heat engines and they need both a hot source of energy and cold region into which they can deposit that energy.energy itself has momentum in the downward direction and cannot contribute to a rocket's upward motion.energy doesn't weigh anything and rockets need weight to propel themselves forward.
hey propel themselves forward by pushing stored mass backward as exhaust.
The feeling of acceleration (our perception of it) is always Group of answer choicesthe same thing as your weight.in the same direction as the real acceleration.in the opposite direction as the real acceleration.at right angles to the real acceleration.
in the opposite direction as the real acceleration.
You make a sharp right turn in your new Ferrari and the bobble-head doll on your dashboard flies out the left side window. The doll's abrupt departure was caused by Group of answer choicesits inertia.its gravitational potential energy.a leftward force exerted on it by the dashboard.a leftward net force it experienced because of the car's velocity.
its inertia.
To propel itself forward, a rocket pushes against Group of answer choicesits own exhaust.the air through which it travels.the launch pad.the earth.
its own exhaust.
A space shuttle flies in orbit 200 miles above the earth's surface. The radius of the earth is 4000 miles. In the cargo bay, the astronauts float in air. Their weight (attraction to the earth) in such an orbit is Group of answer choiceszero.much smaller than their weight on the earth's surface.just slightly smaller than their weight at the earth's surface.much larger than their weight at the earth's surface.
just slightly smaller than their weight at the earth's surface.
You arrive in New Orleans and immediately rent a bike so you can get around town without begging people for rides. Several of your other friends do this as well so you decide to go on a bike ride around the city center. Before starting you decide to play a game where everyone attempts to balance their bicycles while at rest. The person who can balance their bicycle the longest will win a free night out in the french quarter at a Jazz club. You find it extremely difficult to balance the bike. You constantly have to shift your weight left and right attempting to keep the bicycle balanced on the two wheels. In shifting your weight left and right you are: Group of answer choiceskeeping the back and forth movement of the bike centered over the two wheels.keeping the average momentum of your center of mass close to zero.keeping the net force on you and the bicycle averaging around zero.keeping the center of mass exactly over the line connecting the two points where the wheels make contact with the road.
keeping the center of mass exactly over the line connecting the two points where the wheels make contact with the road.
On a giant ferris wheel you stand on a bathroom scale as your car rotates. Your weight registered by the scale will be Group of answer choiceslargest at the bottomlargest at the topalways the sameless than normal
largest at the bottom
The maximum speed of a rocket-propelled spaceship with an exhaust speed of 5000 mph is Group of answer choices2500 mph.5000 mph.limited only by the ratio of fuel to spaceship.10000 mph.
limited only by the ratio of fuel to spaceship.
You go to an amusement park and, being in a physics class, you have connections. The management lets you stand on a scale as you ride a Ferris Wheel that rotates fairly rapidly. You will notice the highest reading on the scale Group of answer choiceson top, because the normal force upwards is weaker than your weight.on top, because the normal force upwards is stronger than your weighton the bottom, because the normal force upwards is weaker than your weight.on the bottom, because the normal force upwards is stronger than your weight.
on top, because the normal force upwards is stronger than your weight-WRONG PROB: on top, because the normal force upwards is weaker than your weight.
When an acrobat tries to balance on top of a unicycle, she pedals the single wheel so as to Group of answer choicesminimize her overall gravitational potential energy.accelerate at a constant rate and minimize her velocity.place its contact point with the ground directly below her overall center of gravity.minimize the torque she exerts on it.
place its contact point with the ground directly below her overall center of gravity.
You're a passenger in a car and you have your eyes closed. The car is traveling at a constant speed on a level road that is turning toward the left. You feel a gravity-like sensation toward your right, but you remain in your car seat. The net force acting on you during this turn Group of answer choicesis zero.points towards your left.points towards your right.points forward.
points towards your left.
It s the holiday break and you decide to take a road trip with your friends to go work in New Orleans building a house for Habitat for Humanity. You have a friend who has a huge Expedition. You and your friends pack up suitcases with your own clothes, and you transport a number of extremely heavy boxes of tools to help with the construction of the houses. The Expedia rides extremely high off the ground and you worry about rolling over the SUV during the trip. To help minimize this possibility you should: Group of answer choices put all the heavy boxes in the luggage rack on the roof. put all the heavy boxes in the back of the SUV on the floor of the cargo area, and the suitcases on top. increase the tire pressure in the tires. decrease the tire pressure in the tires.
put all the heavy boxes in the back of the SUV on the floor of the cargo area, and the suitcases on top.
You can balance a broom upside-down on your hand if you keep Group of answer choicesputting your hand directly below the broom's total potential energy.putting your hand directly below the broom's center of gravity.doing negative work on the broom.increasing the broom's angular momentum.
putting your hand directly below the broom's center of gravity.
In a rocket engine hydrogen and oxygen is burned in a confined chamber to create a hot high pressure gas. The molecules move randomly in all directions at high thermal velocities. When the hot gases flow out of the laval nozzle the Group of answer choicesrandom motions of the hot molecules are converted into directed motion away from the rocket engine.hot gas compresses further and burns again releasing even more energy.hot gas decompresses and the vapor explodes in a fireball.hot gas moves in circles creating a large amount of angular momentum which stabilizes the rocket.
random motions of the hot molecules are converted into directed motion away from the rocket engine.
A child's sipping cup has a round bottom and automatically returns to upright whenever the child tips it. As the cup tips, you can be sure that its center of gravity Group of answer choicesrises and its total potential energy increases.rises and its total potential energy decreases.descends and its total potential energy decreases.descends and its total potential energy increases.
rises and its total potential energy increases.
The weight of an astronaut on a space walk outside the earth-orbiting Space Station is Group of answer choicesthe same as her weight on the earth's surface.zero.slightly less than her weight on the earth's surface.slightly more than zero.
slightly less than her weight on the earth's surface.
A three-wheeled vehicle is Group of answer choicesstatically stable and dynamically unstablestatically unstable and dynamically stableboth statically and dynamically unstableboth statically and dynamically stable
statically stable and dynamically unstable
A classroom demo that is popular with students and unpopular with custodians is to fill a Styrofoam cup with water, poke a hole in the bottom and then drop the cup into a garbage can waiting below. On the way down, the leak will Group of answer choicesstop because the cup doesn't experience gravitystop because the cup and water are both in free fall and locally weightless.increase because the cup is accelerating.increase because gravity pulls on the water more than it does the cup.
stop because the cup and water are both in free fall and locally weightless.
In studying many martial arts, it is necessary to practice efficient and safe postures. One important concept related to how one should stand is that the feet should be reasonably far apart, because Group of answer choicesthe base of support is wider, thus stabilizing the person.the weight on each foot will be less than when standing normally.the weight on each foot will be more than when standing normally.the friction force increases, giving the person more traction.
the base of support is wider, thus stabilizing the person.
Keeping the angular speed constant in circular motion (the number of rotations per second), what happens to the centripetal acceleration as the radius of the circle gets larger? Group of answer choicesthe centripetal acceleration gets smaller.the centripetal acceleration stays the same.the centripetal acceleration gets larger.the centripetal acceleration points outward.
the centripetal acceleration gets larger.
You lose the contest, and the group starts biking. It is a beautiful (but hot!) day, and so you ride your bicycle with no hands on the handle bars. As you go around a gentle turn to the left you are able to stear without touching the handle bars by leaning to the left so that the front wheel turns to the left. This happens because Group of answer choicesthe force of the pavement supporting the front wheel provides a torque which rotates the wheel.leaning left automatically steers the bike to the left.leaning left rotates the front wheel to the left, but there is no torque.static friction against the front wheel rotates the wheel left.
the force of the pavement supporting the front wheel provides a torque which rotates the wheel.
When a sport utility vehicle (SUV) makes a sudden left turn on the highway, it is in danger of flipping over. One valid explanation for this effect is: Group of answer choicesthe SUV's angular mass increases as it turns and its angular momentum decreases. A transfer of angular momentum from its wheels to its frame then causes it to begin rotating so that it flips over.the centrifugal force on the SUV as it goes around the turn pushes outward on the top of the SUV. The wheels are held in place by friction, so only the top of the SUV accelerates outward and it flips over.the leftward frictional force that causes the SUV to accelerate leftward during the turn also exerts a torque on the SUV about its center of mass and can cause the SUV to undergo angular acceleration and flip over.the force of the SUV's momentum pushes it forward while the road pushes it to the left and these two forces twist the SUV so that it undergoes angular acceleration and flips over.
the leftward frictional force that causes the SUV to accelerate leftward during the turn also exerts a torque on the SUV about its center of mass and can cause the SUV to undergo angular acceleration and flip over.
The higher you stand up in a canoe, the higher the overall center of gravity rises. Eventually, the canoe becomes unstable and tips over at the slightest disturbance. That instability develops as soon as Group of answer choicesthe overall center of gravity no longer rises during a tip and instead descends during a tip.the buoyant force exceeds your weight.the canoe's gravitational potential energy exceeds its kinetic energy.the net force on the canoe stops rising and instead begins to decrease.
the overall center of gravity no longer rises during a tip and instead descends during a tip.
During a sharp turn a tricycle (as well as an SUV) can easily flip over because Group of answer choicesthe center of mass gets outside of the area defined by the points of support.the linear momentum gets too large.the static frictional force creates a large torque relative to the center of mass.the rotational mass gets too small.
the static frictional force creates a large torque relative to the center of mass.
It is important for cyclists to lean their bicycles while negotiating sharp turns because Group of answer choicesthe torque created by their leaning balances out the frictional torque from the road which would tend to flip them.the torque created by their leaning balances out their weight and holds them up.their tires flatten out, thus getting better traction on the road.they increase their static stability Flag question: Question 5
the torque created by their leaning balances out the frictional torque from the road which would tend to flip them.
If a rocket fully loaded is 9 parts fuel and 1 part spaceship, the maximum speed that can be obtained is if all of the fuel immediately exits the engine at once. For such a case the rocket would recoil at 9 times the speed of the exhaust gases. However, in a normal rocket the fuel is burned continuously over a period of time. The result of this longer burn is Group of answer choicesthe ultimate speed of the spaceship is less than if the fuel is expelled at once.the ultimate speed of the spaceship is greater than if the fuel is expelled at once.the ultimate speed of the spaceship is the same as if all of the fuel is expelled at once.the ultimate speed of the spaceship is the same as the exhaust.
the ultimate speed of the spaceship is less than if the fuel is expelled at once.
For a ride on the ultimate roller-coaster Danica Spears, a college student from Pensacola takes a ride with one of the blue angels. See the video here: http://www.youtube.com/watch?v=EDzpnufOSTo In the last half of the video the plane makes a high velocity tight turn which is horizontal to the ground and they achieve 7.4 g's of acceleration. During the turn the plane is turned sideways (wings perpendicular to the ground) and the turn is vertical as Danica is situated. She feels herself (and you can see it on her face) pulled strongly to the floor with a gigantic force. What is the actual direction of the force on her (directions are relative to way Danica is facing)? Group of answer choicesin the upwards direction.in the downwards directionin the forward direction.in the rear direction.
the upwards direction
The spin cycle in your washing machine partially dries clothes by spinning them in a perforated metal basket. Such a process works because Group of answer choicesthe water leaves the basket moving tangent to the circular paththe water is forced directly outward from the basketthe water is drawn to the center of the basketthe water is drained by gravity out the bottom of the basket.
the water leaves the basket moving tangent to the circular path
Some engineers have suggested that we can simulate gravity in outer space by having a circular rotating space station where persons feel an outward - directed fictitious force due to the rotation of the station. The reason they feel such a force is because Group of answer choicestheir velocity is toward the center of the space station and their inertia tends to keep them moving outward.the fictitious force is always in the direction of centripetal acceleration.they are accelerating toward the center of the space station and inertia tends to keep them moving sideways.their velocity is away from the center of the space station and their inertia tends to make them move in towards the center.
they are accelerating toward the center of the space station and inertia tends to keep them moving sideways.
Two identical toy rockets are launched simultaneously. One is launched with a rigid surface beneath its rocket engine and the other is launched with nothing but open air beneath its rocket engine. As the two rockets begin to rise upward at launch, Group of answer choicesthey both accelerate upward at the same rate.the rocket with the surface beneath it accelerates upward 1.5 times the rate of the other rocket.the rocket with the surface beneath it accelerates upward at twice the rate of the other rocket.the rocket with the surface beneath it accelerates upward at four times the rate of the other rocket.
they both accelerate upward at the same rate.
You are swinging a bucket full of water around you in a big horizontal circle at a constant speed. You are at the center of its circular path. The net force on the bucket points directly Group of answer choicestoward you.downward.along the bucket's velocity (along its direction of travel).away from you.
toward you.
As the bus you are riding in makes a sharp turn toward the left, you find yourself pressed against the person to your right. The net force you are experiencing as the bus turns left points Group of answer choicestoward your left.forward.toward your right.about half way between forward and toward your right.
toward your left.
You are flying on an airplane and you notice that a ball of aluminum foil from lunch starts to roll to the left. From the motion of the foil ball you can conclude that the plane is Group of answer choicesmoving at constant velocity toward the right.turning toward the left.moving at constant velocity toward the left.turning toward the right.
turning toward the right.
As you ride on a merry-go-round, you feel a strong outward pull that feels just like the force of gravity. This fictitious force occurs because
you are accelerating toward the center of the merry-go-round and experience a fictitious force in the direction opposite your acceleration.
A drop tower is an amusement park ride where you are strapped into a seat, lifted high into the air, and then dropped. While you are in free fall, what is your apparent weight? Group of answer choicesthe same as your actual weight.larger than your actual weight.smaller than your actual weight.zero.
zero.
A rocket is heading upward quickly and a plume of exhaust is streaming downward from its tail. The amount of force that the rocket is exerting on the plume of exhaust is Group of answer choicesless than the amount of force the plume is exerting on the rocket, but not zero.greater than the amount of force the plume is exerting on the rocket.equal to the amount of force the plume is exerting on the rocket.zero.
zero.
