Physics 1111 Final Exam Conceptual Review (Chapters 1-10)
You are pushing a heavy box across a rough floor. When you are initially pushing the box and it is accelerating...
The force that you exert on the box is equal to the force of the box pushing back on you
Michelangelo's assistant has been assigned the task of moving a block of marble using a sled. He says to his boss "when i exert a forward force on the sled, the sled exerts an equal but opposite force backward. So how can i ever start it moving? No matter how hard i pull, the backward reaction force always equals my forward force, so the net force must be zero. Is this correct?
The forces are exerted on different objects. The forward action force is exerted by the assistant on the sled, whereas the backward reaction force is exerted by the sled on the assistant. The sled accelerates forward when the force on it exerted by the assistant is greater than the frictional force exerted backward on it by the ground.
You are trying to push your stalled car. Although you apply a horizontal force of 400 N to the car, it doesn't budge, and neither do you. Which force(s) must also have a magnitude of 400 N?
The friction force exerted by the road on you
A ball is dropped from the top of a tall building. At the same instant, another ball is thrown upward from the ground level. When the two balls pass one another, one on the way up, one on the way down, compare the magnitudes of their acceleration.
The acceleration of both balls is the same
You insert a straw of length l into a tall glass of water. You place your finger over the top of the straw, capturing some air above the water but preventing any additional air from getting in or out, and then you lift the straw from the water. You find that the straw retains most of the water. Does the air in the space between your finger and the top of the water have a pressure that is greater than, equal to, or less than the atmospheric pressure outside the straw?
The air pressure inside the straw a the top to be less than the atmospheric pressure outside the straw.
How does doubling the speed of something affect the work being done?
If the speed is doubled, the object has four times as much kinetic energy and is therefore capable of doing four times as much work.
On a rotating carousel or merry-go-round, one child sits on a horse near the outer edge and another sits on a lion halfway out from the center. (a) which child has the greater linear velocity? (b) which child has the greater angular velocity?
(a) Linear velocity is the distance traveled divided by the time interval. The child at the outer edge has the greater linear velocity (on the horse) (b) Angular velocity is the angle of rotation of the carousel as a whole divided by the time interval. The two children have the same angular velocity
A rider on a Ferris wheel movies in a vertical circle of radius r at constant speed v. Is the normal force that the seat exerts on the rider at the top of the wheel (a) less than (b) more than (c) or the same as, the force the seat exerts at the bottom of the wheel
(a) less than
If the kinetic energy of a baseball is doubled, by what factor has its speed increased? If its speed is doubled, by what factor does its kinetic energy increase?
(a) square root of 2 (b) factor of 4
A car moves along the x axis. What is the sign of the car's acceleration if it is moving in the positive x direction with: (a) increasing speed (b) decreasing speed What is the sign of the acceleration if the car moves in the negative x direction with (c) increasing speed (d) decreasing speed
(a): positive (b): negative (c): negative (d): positive
Two satellites orbit the Earth in circular orbits of the same radius. One satellite is twice as massive as the other. Which statement is true about the speeds of these satellites?
(b) The two satellites have the same speed.
A space shuttle in orbit around the Earth carries its payload with its mechanical arm. Suddenly, the arm malfunctions and releases the payload. What will happen to the payload?
(c) It will remain in the same orbit with the shuttle.
A skier starts from rest at the top of each of the hills shown in the figure. On which hill will the skier have the highest speed at the bottom assuming a small amount of friction:
(c) see page 163
In the International Space Station which orbits Earth, astronauts experience apparent weightlessness because
(c) the astronauts and the station are in free fall towards the center of the earth.
A penny is placed on a turntable which is spinning clockwise. If the power to the turntable is turned off, which arrow best represents the direction of the acceleration of the penny at point P while the turntable is still spinning but slowing down?
(d) down and to the right
The moon does not crash into the Earth because:
(d) it is freely falling but it has a high tangential velocity.
Which of the following should be part of solving any problem in physics? Select all that apply.
-Read the problem carefully -Draw a picture of the situation -Write down the variables that are given -Think about which physics principles to apply -Determine which equations can be used to apply the correct physics principles -Check the units when you have completed your calculation -Consider whether the answer is reasonable or not
What approximately is the percent uncertainty in the measurement 5.45 +/- 0.25 m
.25/5.48 x 100 = 4.5%
What are the two conditions for equilibrium?
1. If a particular force component points along the negative x or y axis, it must have a negative sign 2. the sum of all torques acting on an object, as calculated about any axis, must be zero.
An object at rest begins to rotate with a constant angular acceleration. If this object rotates through an angle θ in time t, through what angle did it rotate in the time 1/2 t?
1/4θ.
You are in the middle of a large field. You walk in a straight line for 100 m, then turn left and walk 100 m more in a straight line before stopping. When you stop, you are 100 m from your starting point. By how many degrees did you turn?
120°
Four students use different instruments to measure the length of the same pen. Which measurement implies the greatest precision?
160.0 mm
The number 0.0078 has how many significant figures?
2
A 50-N crate sits on a horizontal floor where the coefficient of static friction between the floor is 0.50. A 20-N force is applied to the crate acting to the right. What is the resulting static friction force acting on the crate?
20 N to the left
How many significant figures does 1.362 + 25.2 have?
3
A car accelerates from rest to 30 km/h. Later, on a highway it accelerates from 30 km/h to 60 km/h. Which takes more energy, going from 0 to 30, or from 30 to 60?
30 to 60 km/h
You are adding vectors of length 20 and 40 units. What is the only possible resultant magnitude that you can obtain out of the following choices? 1) 0 2) 18 3) 37 4) 64 5) 100
37 because the minimum resultant will occur when the vectors are going in opposite directions and the resultant is 20. The maximum resultant will occur when the vectors are going in the same direction and the resultant is 60. So the possible resultant has to be in the middle
When the speed of your car is doubled, by what factor does its kinetic energy increase?
4
A car traveling at a velocity v can stop in a minimum distance d.What would be the car's minimum stopping distance if it were traveling at a velocity of 2v?
4(d)
A car starts from rest and accelerates at a constant 10 m/s^2 during a 1/4 mile (402 m) race. How fast is the car going at the finish line?
90 m/s
In which of the following cases does a car have a negative velocity and a positive acceleration?
A car that is traveling in the -x direction and decreasing in speed
Suppose two vectors each have length 3.0 units. What is the range of possible lengths for the vector representing the sum of the two?
A magnitude between 0 and 6 depending on the directions.
Suppose you are standing on the edge of a large freely moving turntable. If you walk toward the center...
The turntable speeds up
Archimedes' Principle
the bouyant force on an object is equal to the weight of the fluid displaced by the object
If the velocity of an object is zero, does it mean that the acceleration is zero? If the acceleration is zero, does it mean that the velocity is zero?
A zero velocity does not mean necessarily that the acceleration is zero, nor does zero acceleration mean that the velocity is zero: a car with initial velocity of zero accelerates, which means that the acceleration is not zero since the velocity of the car changes. Or, as you cruise a long a straight highway at a constant velocity of 100 km/h you acceleration is zero.
What points toward the center of the circle in uniformed accelerated motion?
Acceleration, net force
Which of the following point towards the center of the circle in uniform circular motion?
Acceleration, net force
A rocket is shot into the air. At the moment the rocket reaches its highest point, a horizontal distance d from its starting point, a prearranged explosion separates it into two parts of equal mass. Part I is stopped in midair by the explosion, and it falls vertically to Earth. Where does part II land?
After the rocket is fired, the path of the CM of the system continues to follow the parabolic trajectory of a projectile acted on by a constant g. The CM will thus land at a point 2d from the starting point. Since the masses of I and II are equal, the CM must be midway between them at any time. Therefore, part II lands at a distance 3d from the starting point.
[L^2] represents the dimensions for:
All of the above: Cm^2, square feet, m^2
What is your instantaneous speed at the instant you turn around to move in the opposite direction?
Always zero: A change in magnitude and direction
A bullet fired from a rifle begins to fall...
As soon as it leaves the barrel
A child whirls a ball in a vertical circle. Assuming the speed of the ball is constant (an approximation), when would the tension in the cord connected to the ball be greatest?
At the bottom of the circle
A mover is trying to lift a piano (slowly) up to a second-story apartment. He is using a rope looped over two pulleys as shown. What force must he exert on the rope to slowly lift the piano's 1600-N weight?
Because of F=ma the piano mover can exert a force equal to half of the piano's weight.
Two satellites orbit the Earth at the same radius. One satellite is twice as massive as the other. Which statement is true about the speeds of these satellites?
Both have the same speed
Two balls are thrown off a building with the same speed, one straight up and one at a 45 ∘ angle. Which statement is true if air resistance can be ignored?
Both hit the ground with the same speed
You drop a rock off a bridge. When the rock has fallen 4 m, you drop a second rock. As the two rocks continue to fall, what happens to their velocities?
Both increase at the same time.
Consider two identical pails of water filled to the brim. One pail contains only water, the other has a piece of wood floating in it. Which pail has the greater weight?
Both pails weigh the same. Archimedes principle says that the wood displaces a volume of water with weight equal to the weight of the wood.
A car drives at steady speed around a perfectly circular track.
Both the acceleration and the net force on the car point inward
Which pulls harder gravitationally, the Earth on the Moon, or the Moon on the Earth? Which accelerates more?
Both the same; the moon
A boy on a small hill aims his water-balloon slingshot horizontally, straight at a second boy hanging from a tree branch a distance d away. At the instant the water balloon is released, the second boy lets go and falls from the tree, hoping to avoid being hit. Show that he made the wrong move. Ignore air resistance.
Both the water balloon and the boy in the tree start falling at the same instant, and in a time t they fall in the same vertical distance. In the time it takes the water balloon to travel the horizontal distance, d, the balloon will have the same position y as the falling boy. If he would have stayed in the tree he would not have been hit.
Two balls are thrown from a cliff. One is thrown directly up, the other directly down. Both balls have the same initial speed, and both hit the ground below at different times. Which ball hits the ground at the greater speed?
Both will have the same speed
You can hold a box against a rough wall and prevent it from slipping down by pressing hard horizontally. How does the application of a horizontal force keep the object from moving vertically?
By the help of friction
Consider a force F=80N applied to a beam as shown in the figure below. The length of the beam is ℓ=5.0m, and θ=37∘, so that x=3.0m and y=4.0m.
Equations τ = rFsinθ show that there are three ways in which the torque can be written. It can be the product of the force, the lever arm, and the sine of the angle between them
Newton's first law of motion
Every object continues in a state of rest or of uniform speed in a straight line unless acted on by a nonzero net force Law of Inertia (tendency for an object to maintain its state of rest or of uniform velocity in a straight line)
A ball is thrown straight up. At what point does the ball have the most energy? Ignore air resistance.
Everywhere; the energy of the ball is the same at all points
A ball is thrown straight up. Consider its motion from the moment it leaves your hand to the moment just before it hits the ground. At what point doe the ball have the most total energy?
Everywhere; the energy of the ball is the same at all points on its bath.
Newton's Second law of motion
F = ma The acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object. The direction of the acceleration is in the direction of the net force acting on the object. -The rate of change of momentum of an object is equal to the net force applied to it
How long would it take you to stop a moving car that is going twice as fast...
Four times the distance to stop
What makes a car go forward?
Friction is needed to make the wheels go around. On firm ground, the tires push backward against the ground because of friction. By Newton's third law, the ground pushes on the tires in the opposite direction, accelerating the car forward.
Water flows in a horizontal pipe that is narrow but then widen and the speed of the water becomes less. The pressure in the water moving in the pipe is
Greater in the wide part and greater where the speed is lower
Bonnie sits on the outer rim of a merry-go-round, and Jill sits midway between the center and the rim. The merry-go-round makes one complete revolution every 2 seconds. Jill's linear velocity is:
Half of Bonnie's
Principle of conservation of mechanical energy
If only conservative forces do work, the total mechanical energy of a system neither increases nor decreases in any process. It stays constant—it is conserved.
A child sits upright in a wagon which is moving to the right at a constant speed. The child extends her hand and throws an apple straight upward, while the wagon continues to travel forward at a constant speed. If air resistance is neglected, will the apple land (a) behind the wagon, (b) in the wagon, or (c) in front of the wagon?
In the wagon
You are riding in an enclosed train car at 90 km/h. If you throw a baseball straight up, where will the baseball land?
In your hand
If there were a great migration of people toward the Earth's equator, the length of the day would
Increase because of the conservation of angular momentum
A bear sling is used in some national parks for placing backpackers' food out of the reach of bears. As the backpacker raises the pack by pulling down on the rope, the force F needed...
Increases, but the rope always sags where the pack hangs
A small mass m on a string is rotating without friction in a circle. The string is shortened by pulling it through the axis of rotation without any external torque (Figure 1) . What happens to the angular velocity of the object?
It increases
A small mass m on a string is rotating without friction in a circle. The string is shortened by pulling it through the axis of rotation without any external torque, see the figure What happens to the tangential velocity of the object?
It increases
Is the normal force always perpendicular to an inclined place? Is it always vertical?
It is always perpendicular to an inclined plane yet it is not always vertical.
A school bus comes to a sudden stop, and all of the backpacks on the floor start to slide forward. What force causes them to do that?
It isn't "force" that does it. By Newton's first law, the backpacks continue in their state of motion, maintaining their velocity. The backpacks slow down if a force is applied, such as friction with the floor.
A Ping-Pong ball is shot into a circular tube that is lying flat (horizontal) on a tabletop. When the ball exits the tube, which path will it follow?
It will follow its path of (c): straight
A rowboat is carrying a large granite rock that is floating in a small lake. If the rock is thrown overboard and sinks, does the lake level drop, rise, or stay the same?
Less lake water is displaced and the water level of the lake drops when the rock is in the lake
You drive 4 km at 30 km/h and then another 4 km at 50 km/h. What is your average speed for the whole 8-km trip? a. More than 40 km/hr b. Less than 40 km/hr c. Equal to 40 km/hr d. Not enough info
Less than 40 km/h
To pull an old stump out of the ground, you and a friend tie two ropes to the stump. You pull on it with a force of 500 N to the north while your friend pulls with a force of 450 N to the northwest. The total force from the two ropes is...
Less than 950 N
When a skier skis down a hill, the normal force exerted on the skier by the hill is...
Less than the weight of the skier
As water flows from a low elevation to a higher elevation through a pipe that changes in diameter,
Need more information to determine how the water pressure changes.
Can kinetic energy be negative?
No
To negotiate a flat curve at a faster speed, a driver puts a couple of sand bags in his van aiming to increase the force of friction between the tires and the road. Will the and bags help?
No
Two identical billiard balls traveling at the same speed have a head-on collision and rebound. If the balls had twice the mass, but maintained the same size and speed, how would the rebound be different?
No difference
Two identical billiard balls traveling at the same speed have a head-on collision and rebound. If the balls had twice the mass but maintained the same size and incoming speed, how would the rebound be different?
No difference from the first case.
A truck is traveling horizontally to the right. When the truck starts to slow down, the crate on the truck bed starts to slide. In what direction could the net force be on the crate?
No direction. The net force is zero.
Suppose you watch a cup slide on the (smooth) dashboard of an accelerating car from an inertial reference frame outside of the car, on the street. From your inertial frame, Newton's laws are valid. What forces push the cup off the dashboard?
No force is needed. The car accelerates out from under the cup, which tends to remain at rest. Newton's First Law.
A bowling ball is dropped from a height h onto the center of a trampoline, which launches the ball back up into the air. How high will the ball rise?
No more than h-probably a little less
A satellite in circular orbit around the Earth moves at constant speed. This orbit is maintained by the force of gravity between the Earth and the satellite, yet no work is done on the satellite. How is this possible?
No work is done if the direction of motion is perpendicular to the force
Hot air is less dense than cold air. Could a hot-air balloon be flown on the Moon, where there is no atmosphere?
No, there is no cold air to displace, so no buoyancy force would exist.
The bar is being used as a lever to pry up a large rock. The small rock acts as a fulcrum. The force required at the long end of the bar can be quite a bit smaller than the rock's weight, mg, since it is the torques that balance in the rotation about the fulcrum. If, however, the leverage isn't sufficient, and the large rock is not budged, what are two ways to increase the lever arm?
One way is to increase the bar/ lever arm at the end thereby pushing with a larger lever arm. A second way is to move the fulcrum closer to the large rock.
A 10.0 kg box is dragged on a horizontal friction-less surface by a horizontal force of 10.0 N. If the applied force is doubled, the normal force on the box will...
Remain the same.
If you used 1000 J of energy to throw a ball, would it travel faster if you threw the ball (ignoring air resistance)
So that it was not rotating
Suppose you are sitting on a rotating stool holding a 2- mass in each outstretched hand. If you suddenly drop the masses, your angular velocity will
Stay the same
Why does an ocean liner float?
The average density of the ocean liner is less than that of seawater.
A bowling ball hangs from a 1.0-m-long cord, (Figure 1) : (i) A 200-gram putty ball moving 5.0 m/s hits the bowling ball and sticks to it, causing the bowling ball to swing up; (ii) 200-gram rubber ball moving 5.0 m/s hits the bowling ball and bounces straight back at nearly 5.0 m/s, causing the bowling ball to swing up. Part A Describe what happens.
The ball swings up farther in (ii) than in (i). the two negative signs cancel so the change in momentum is bigger.
A baseball is pitched horizontally toward home plate with a velocity of 110 km/h. In which of the following scenarios does the baseball have the largest change in momentum? The catcher catches the ball. The baseball is hit straight back to the pitcher at a speed of 110 km/h. The ball is popped straight up at a speed of 110 km/h. Scenarios "The catcher catches the ball." and "The ball is popped straight up at a speed of 110 km/h." have the same change in momentum. Scenarios "The catcher catches the ball.", "The ball is popped straight up at a speed of 110 km/h.", and "The baseball is hit straight back to the pitcher at a speed of 110 km/h." have the same change in momentum
The baseball is hit straight back to the pitcher at a speed of 110 km/h. What is the ball popped straight up?
A woman stands up in a rowboat and walks from one end of the boat to the other. How does the boat move, as seen from the shore?
The boat moves in the opposite direction.
A hunter is aiming horizontally at a monkey who is sitting in a tree. The monkey is so terrified when it sees the gun that it falls from the tree. At that very instant, the hunter pulls the trigger. What will happen?
The bullet will hit the monkey because both the monkey and the bullet are falling downward at the same rate due to gravity
While driving fast around a sharp right turn, you find yourself pressing against the car door. What is happening?
The door is exerting a rightward force on you
A person stands on a scale in an elevator. His apparent weight will be the greatest when...
The elevator is accelerating upward.
You are trying to push a stalled car. Although you apply a horizontal force of 400 N to the car, it doesn't budge and neither do you. Which force must also have a magnitude of 400 N?
The force exerted by the car on you The friction exerted by the car on the road The friction force exerted by the road on you
A golf ball is hit with a golf club. While the ball flies through the air, which forces act on the ball? Neglect air resistance...
The force of gravity acting on the ball
What causes the boat in the picture to move forward?
The force that the water exerts on the paddle
A golf ball and an equal-mass bean bag are dropped from the same height and hit the ground. The bean bag stays on the ground while the golf ball rebounds. Which experiences the greater impulse from the ground? The golf ball. The bean bag. Both the same. Not enough informatio
The golf ball. difference in final and initial velocity, initial-final. Impulse = change in momentum bean bag final is zero, so impulse is simply initial. because the golfball rebounds it has a final P that is in the opposite direction as the initial, therefore 2 negatives cancel. And you get a greater impulse
A car travels along the x-axis with increasing speed. We don't know to the left or to the right. Which of the graphs most closely represents the motion of the car?
The graph that concave down
In the picture, Matt is able to move the truck because...
The ground exerts a greater friction force on Matt than it does on the truck
Two spheres have the same radius and equal mass. One sphere is solid, and the other is hollow and made of a denser material. Which one has the bigger moment of inertia about an axis through its center?
The hollow one.
A small solid sphere and a small thin hoop are rolling along a horizontal surface with the same translational speed when they encounter a 20 ∘ rising slope. Part A If these two objects roll up the slope without slipping, which will rise farther up the slope?
The hoop
Several objects roll without slipping down an incline of vertical height H, all starting from rest at the same moment. The objects are in a thin hoop (plain wedding band), a spherical marble, a solid cylinder, and an empty soup can. In addition, a greased box slides down without friction. In what order do they reach the bottom of the incline?
The hoop has the largest moment of inertia and will have the lowest speed and will arrive at the bottom behind the solid cylinder, which in turn will be behind the marble. The empty can, which is mainly a hoop plus a thin disk, will be a bit faster than the pure hoop but slower than the solid cylinder.
A baseball is hit high and far. Which of the following statements is true? At the highest point...
The magnitude of the velocity is the slowest
A baseball is hit high and far. Which of the following statements is true? At the highest point,
The magnitude of the velocity is the smallest (the ball is traveling the slowest)
Two water slides at a pool are shaped differently, but start at the same height. Two riders start from rest at the same time on different slides. (a) which rider is traveling faster at the bottom? (b) which rider makes it to the bottom first? Ignore friction and assume both slides have the same path length
The mass cancels and so the speed will be the same, regardless of the mass of the rider. Since they descend at the same vertical height, they will finish with the same speed. The person with less potential energy converted to kinetic will reach the bottom first, although traveling the same speed.
One ball is dropped vertically from a window. At the same time, a second ball is thrown horizontally from the same window. Which ball has the greater speed at ground level?
The thrown ball
Law of conservation of angular momentum
The total angular momentum of a rotating object remains constant if the net torque acting on it is zero.
Law of conservation of energy
The total energy is neither increased nor decreased in any process. Energy can be transformed from one object to another, but the total amount remains constant.
If you double the muzzle velocity of a cannon, how does the range change of the cannon?
The maximum range will increase by a factor of 4
What is mass?
The measure of inertia of an object
What is the work-energy principle?
The net work done on an object is equal to the change in the object's kinetic energy -If positive net work (w) is done on an object, the object's kinetic energy increases by amount W.
At time t=o an object is traveling to the right along the +x axis at a speed of 10 m/s with acceleration -2 m/s². Which statement is true...
The object will slow down momentarily stopping, then pick up speed moving to the left.
A dam holds back a lake that is 85 m deep at the dam. If the lake is 20 km long, how much thicker should the dam be than if the lake where smaller, only 1.0 km long?
The same. Pressure depends on depth, not length.
The normal force on an extreme skier descending a very steep slope can be zero if...
The slope is vertical 90°
Law of conservation of momentum
The total momentum of an isolated system of objects remains constant
Two wheels having the same radius and mass rotate at the same angular velocity ((Figure 1) ). One wheel is made with spokes so nearly all the mass is at the rim. The other is a solid disk. How do their rotational kinetic energies compare?
The wheel with spokes has about twice the KE.
Which of the three kicks in the figure is in the air for the longest amount of time? They all reach the same maximum height, h. Ignore air resistance...
They are all the same
A truck going 15 km/h has a head-on collision with a small car going 30 km/h. The car has the greater change of momentum because it has the greater speed. The truck has the greater change of momentum because it has the greater mass. They both have the same change in magnitude of momentum because momentum is conserved. Neither the car nor the truck changes its momentum in the collision because momentum is conserved. None of the above is necessarily true.
They both have the same change in magnitude of momentum because momentum is conserved
A tennis ball collides head-on with a more massive baseball. Which ball experiences the greater force of impact? Which experiences the greater acceleration during the impact? Which of Newton's laws are useful to obtain this correct answer?
They both have the same force of impact The tennis ball experiences the greater acceleration during impact Newton's second and third law.
You hold a piece of wood in one hand and a piece of iron in the other. Both pieces have the same volume, and you hold them fully under water at the same depth. At the moment you let go of them, which one experiences the greater buoyancy force?
They experience the same buoyancy force.
The solid dot shown in the figure below is a pivot point. The board can rotate about the pivot.
Torque is the product of the lever arm and the component of the force perpendicular to the arm. Although the 1000 N force has the greatest magnitude, it acts at the pivot and so the lever arm is zero, and thus the torque is also zero. The 800 N force is parallel to the lever arm and also exerts no torque. Of the three 500 N forces, (c) is both perpendicular to the lever arm and farthest from the pivot.
Newton's Third Law of Motion
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. For every action there is an equal but opposite reaction.
You push on a heavy desk, does it always push back on you?
Yes
Can a small sports car ever have the same momentum as a large sport-utility vehicle with three times the sport's car's mass?
Yes if the small sport's car's speed is three times greater
You are holding a spinning bicycle wheel while standing on a stationary turntable. If you suddenly flip the wheel over so that it is spinning in the opposite direction, the turntable will... If it is only flipped horizontally, at a 90° angle, what will happen?
You and the wheel will begin revolving in the same direction the wheel was spinning originally The same as above, just slower
Your little sister wants you to give her a ride on her sled. On level ground, what is the easiest way to accomplish this?
You exert less force if you full her because the friction force is proportional to the normal force.
a ball is thrown straight up. neglecting air resistance, which statement is NOT true regarding the energy of the ball?
a. the potential energy decreases while the ball is going up
Which statements are not valid for a projectile? Take up as positive: (a) the projectile has the same x velocity at any point on its path (b) the acceleration of the projectile is positive and decreasing when the projectile is moving upwards, zero at the top, and increasingly negative as the projectile descends (c) the acceleration of the projectile is a constant negative value (d) The y component o the velocity of the projectile is zero at the highest point of the projectile's path (e) the velocity at the highest point is zero
b) The acceleration of the projectile is positive and decreasing when the projectile is moving upwards, zero at the top, and increasingly negative as the projectile descends e) The velocity at the highest point is zero
A ball is thrown downward at a speed of 20 m/s. Choosing the +y axis pointing upward and neglecting air resistance, which equation(s) could be used to solve for other variables? The acceleration due to gravity is g=9.8 m/s² downward.
b) y = y₀ +( -20 m/s)t - (1/2)gt² c) v² = (20 m/s)² - 2g(y-y₀)
A skier starts from rest at the top of each of the hills shown in the figure. On which hill will the skier have the highest speed at the bottom if we ignore friction:
both (c) and (d) equally ( see page 163 )
a man pushes a block up an incline at a constant speed. as the block moves up the incline, a. its kinetic energy and potential energy both increase b.its kinetic energy increases and its potential energy remains the same c.its potential energy increases and its kinetic energy remains the same d.its potential energy increases and its kinetic energy decreases by the same amount
c.its potential energy increases and its kinetic energy remains the same
Suppose an object is accelerated by a force of 100 N. Suddenly a force of 100 N in the opposite direction is exerted on the object, so that the forces cancel. The object...
continues at the velocity that it had before the second force was applied
A small boat coasts at constant speed under a bridge. A heavy sack of sand is dropped from the bridge onto the boat. The speed of the boat
decreases: if mass goes up, velocity will go down if momentum is conserved.
A baseball player hits a ball that soars high into the air. After the ball has left the bat, and while it is traveling upward, what is the direction of acceleration? Ignore air resistance...
downward direction
A rowboat floats in a swimming pool, and the level of the water at the edge of the pool is marked. The boat is removed from the water. The level of the water will
fall
you push a heavy crate down a ramp at a constant velocity. only four forces act on the crate. which force does the greatest magnitude of work on the crate?
force of friction
Accuracy represents
how close a measurement is to its true value
Which is not true about an order-of-magnitude estimation?
it will always be accurate to at least two significant figures
A car travels 10 m/s east. Another car travels 10 m/s north. The relative speed of the first car with respect to the second is...
less than 20 m/s
The magnitude of a component of a vector must be
less than or equal to the magnitude of the vector
A railroad tank car contains milk and rolls at a constant speed along a level track. The milk begins to leak out the bottom. The car then The car then slows down. speeds up. maintains a constant speed. Need more information about the rate of the leak.
maintains a constant speed
To convert from ft^2 to yd^2 you should
multiply by 1/9
You push very hard on a heavy desk, trying to move it. You do work on the desk:
only if it starts moving.
A student's weight displayed on a digital scale is 117.2 lb. This would suggest that her wight is:
somewhere between 117.0 and 117.4
Beaker A is filled to the brim with water. Beaker B is the same size and contains a small block of wood which floats when the beaker is filled with water to the brim. Which beaker weighs more?
the same for both
A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point in its path?
v=0, a= 9.8 m/s² down
A car speedometer that is supposed to read the linear speed of the car uses a device that actually measures the angular speed of the tires. If larger-diameter tires are mounted on the car instead, how will that affect the speedometer reading?
will read low. if r increased then v will increase, but angular velocity will stay constant
