The diagram below is a top-down view of two children pulling a 10.7-kg sled along the snow. The first child exerts a force of F1 = 16 N at an angle θ1 = 45° counterclockwise from the positive x direction. The second child exerts a force of F2 = 6 N at an angle θ2 = 30° clockwise from the positive x direction.
(a) Find the magnitude and direction of the friction force acting on the sled if it moves with constant velocity.
(b) What is the coefficient of kinetic friction between the sled and the ground?
(c) What is the magnitude of the acceleration of the sled if F1 is doubled and F2 is halved in magnitude?
In: Physics
"A mass, denoted M, slides downward along a rough plane surface inclined at angle of 25.94 in degrees relative to the horizontal. Initially the mass has a speed of 7.51 m/s, before it slides a distance of 1.0 m down the incline. During this sliding, the magnitude of the power associated with the work done by friction is equal to the magnitude of the power associated with the work done by the gravitational force. What is the coefficient of kinetic friction between the mass and the incline?"
Edit: After some more studying, I found out the answer. However, since I don't know how to remove a question, please work I out so that others (and myself) will know for future reference.
In: Physics
An attacker at the base of a castle wall 3.75 m high throws a rock straight up with speed 8.50 m/s from a height of 1.50 m above the ground.
(a) Will the rock reach the top of the wall?
(b) If so, what is its speed at the top? If not, what initial speed must it have to reach the top?
(c) Find the change in speed of a rock thrown straight down from the top of the wall at an initial speed of 8.50 m/s and moving between the same two points.
(d) Does the change in speed of the downward-moving rock agree with the magnitude of the speed change of the rock moving upward between the same elevations?
(e) Explain physically why it does or does not agree.
In: Physics
Match the right choice with the right question by placing the right letter in the far left column. The letters go with the questions.
|
Mark |
Choices |
Letter |
Questions |
|
Boiling Point |
A |
Moves heat from cold reservoir to a hot reservoir |
|
|
Convection |
B |
In this process the volume remain constant. |
|
|
Radiation |
C |
The sum of the Kinetic and Potential energies of the particles in a system. |
|
|
Kelvin |
D |
The amount of heat necessary to change a liquid to a gas at constant temperature is the __________. |
|
|
Efficiency |
E |
The amount of heat necessary to change a liquid to a solid at constant temperature is the ___________. |
|
|
Heat Engine |
F |
The amount of heat necessary to change the temperature of 1 kg of a substance 10 Celsius is |
|
|
Melting Point |
G |
Heat transfer that involves mass movement is _______________ |
|
|
Entropy |
H |
In this process the temperature remain constant. |
|
|
Refrigerators |
I |
A tile floor feels colder than a rug on bare feet because the tile has a greater ______________. |
|
|
Latent heat of vaporization |
J |
A process where no heat is transferred into or out of a system. |
|
|
Thermal conductivity |
K |
Sun's rays are transmitted to Earth |
|
|
Triple-point |
L |
Charle’s Law is a ________ process. |
|
|
Specific heat |
M |
The first law of thermodynamics states that heat added to a closed system can change the internal energy of the system and/or do ______________. |
|
|
Internal Energy |
N |
The temperature at which a substance changes from a gas to liquid |
|
|
Latent heat of fusion |
O |
Zero degrees Celsius |
|
|
Isothermal |
P |
A pressure and temperature where a substance exist as a solid, liquid, and gas. |
|
|
Isobaric |
Q |
In the gas laws, the ______________ temperature scale must be used |
|
|
Isochoric |
R |
Disorder is always increasing in the universe, which shows _______ is always increasing. |
|
|
Adiabatic |
S |
Moving heat from a hot reservoir to a cold reservoir to do work. |
|
|
Work |
T |
The amount of work that comes out of an engine divided by the amount of heat put into an engine. |
In: Physics
a. Consider a capacitor being charged by a battery in a simple RC circuit. After a switch is thrown to charge the capacitor, when is the battery delivering the most power? It is when immediately after the switch is thrown. Not when the capacitor is fully charged or half charged. Why? Please explain in detail. b. After a switch is thrown to charge the capacitor, the capacitance is constant regardless of if it is fully or half charged or if it is immediately when the switch is thrown. Why? Please explain in detail. After a switch is thrown to charge the capacitor, when is the electric field greatest in the capacitor gap? Once the capacitor is fully charged. Why?
In: Physics
Two loudspeakers are about 10 m apart in the front of a large classroom. If either speaker plays a pure tone at a single frequency of 400 Hz, the loudness seems pretty even as you wander around the room, and gradually decreases in volume as you move farther from the speaker. If both speakers then play the same tone together, what do you hear as you wander around the room?
| The sound is louder but maintains the same relative spatial pattern of gradually decreasing volume as you move away from the speakers. | |
| The pitch of the sound increases to 800 Hz, and the sound is louder but not twice as loud. It is louder closer to the speakers and gradually decreases as you move away from the speakers−except near the back wall, where a slight echo makes the sound louder. | |
| As you move around the room, some areas seem to be dead spots with very little sound, whereas other spots seem to be louder than with only one speaker. | |
| The sound is twice as loud−so loud that you cannot hear any difference as you move around the room. | |
| At points equidistant from both speakers, the sound is twice as loud. In the rest of the room, the sound is the same as if a single speaker were playing. |
In: Physics
12. Your friend with great excitement tells you about his newest idea to solve the energy crisis: He wants to use an electromotor to drive a generator and then use part of the electric power generated to power the electromotor while using the rest to power his home. What would you tell him?
In: Physics
A man on a road trip drives a car at different constant speeds over several legs of the trip. He drives for 50.0 min at 55.0 km/h, 15.0 min at 65.0 km/h, and 45.0 min at 45.0 km/h and spends 20.0 min eating lunch and buying gas.
(a)
What is the total distance traveled over the entire trip (in km)?
(b)
What is the average speed for the entire trip (in km/h)?
In: Physics
What does a finite length 2D sinusoidal standing wave with one node look like?
What does a finite length 3D sinusoidal standing wave with one node look like
In: Physics
What are some examples of supersonic wings?
|
Double-wedge airfoil |
||
|
Thick cambered airfoils |
||
|
Swept wings |
||
|
All of the above |
||
|
A and C above |
In: Physics
A 4.70 kg block hangs from a spring with spring constant 2300 N/m . The block is pulled down 5.50 cm from the equilibrium position and given an initial velocity of 1.10 m/s back toward equilibrium.
1) What is the frequency of the motion?
2) What is the amplitude?
3) What is the total mechanical energy of the motion?
In: Physics
In: Physics
On a frictionless air table, Puck A with mass ?A = 0.120 kg is moving at speed ?A = 2.80 m/s in the +? direction when at the origin it hits Puck B (of mass ?B = 0.140 kg), which is initially at rest. Puck A is deflected in the collision into a final velocity of ?'A = 2.10 m/s at an angle of 30° from the + ? axis. The collision is not elastic.
a) Write down equations expressing conservation of momentum in both the ? and ? directions.
b) Solve the equations for velocity (?'B, ?'B) of Puck B.
c) What fraction of the initial kinetic energy is lost in this collision?
In: Physics
In: Physics
A 1.08 kg copper rod rests on two horizontal rails 0.84 m apart and carries a current of 60 A from one rail to the other. The coefficient of static friction between rod and rails is 0.53. What is the smallest magnetic field (not necessarily vertical ) that would cause the rod to slide?
A) What is the angle of B from the vertical? (deg)
B) What is the magnitude of B?
In: Physics