Two boxes with masses m1=5.0 kg and m2=3.0 kg are connected by a massless rope, which is put over a massless, frictionless pulley. The coefficient of kinetic friction between the incline and the boxes is 0.12 and the coefficient of static friction between the incline and the boxes is 0.25.The angles of the inclines with respect to the horizontal are ?=45** and ?2=30**. Use 9.8 m/s^2 for gravity and assume the incline is fixed in space.
a.) Show that the system will have a nonzero acceleration if it is initially at rest. Find the magnitude and direction of acceleration.
b.) If the system moves 1.5 m(in the direction found in part a), what is the work done by: i.) gravity on m1, ii.) the normal force on m1, iii.) friction on m1, iv.) gravity on m2, v.) the normal force on m2, vi.) friction on m2
c.) Using the results from part b, what is the speed of the system after it has moved 1.5 m if it was initially at rest?
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Explain in your own words the transformations that occur at constant pressure and temperature; include all the relevant diagrams.
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Under constant pressure, the temperature of 2.00 mol of an ideal monotomic gas is raised 15.0 K. What are a) the work done by the gas b) energy transferred as heat Q c) the change Delta-Eint in the internal energy of the gas, and d) the change Delta-K in the average kinetic energy per atom
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A turntable that spins at a constant 77.0 rpm takes 3.50 s to reach this angular speed after it is turned on. Find its angular acceleration (in rad/s^2), assuming it to be constant, and the number of degrees it turns through while speeding up.
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A capacitor C is connected to a battery of V volts and is fully charged.Keeping the battery connected, the spacing between the capacitor plates is reduced to half.
What happens to the potential difference between the two plates? Why?
What happens to the charge on the capacitor? Why?
What happens to the energy stored in the capacitor? Why?
Now the battery is disconnected, and then the plate spacing is restored to its original value.
What happens to the potential difference between the two plates? Why?
What happens to the charge on the capacitor? Why?
What happens to the energy stored in the capacitor? Why?
Note: It is not enough if you say
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A 48 g ice cube at -59°C is placed in a lake whose temperature is 57°C. Calculate the change in entropy of the cube-lake system as the ice cube comes to thermal equilibrium with the lake. The specific heat of ice is 2220 J/kg·K. (Hint: Will the ice cube affect the temperature of the lake?)
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An object acted on by three forces moves with constant velocity. One force acting on the object is in the positive x direction and has a magnitude of 7.0 N ; a second force has a magnitude of 4.8 N and points in the negative y direction.
a) Find the magnitude of the third force acting on the object.
b) Find the direction of the third force acting on the object.
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In February 2013, a 10,000 ton meteor entered the atmosphere near the city of Chelyabinsk, Russia. Analysis of the trajectory showed that the meteor was traveling at a speed of 17.5 km/s at an angle of 17.7o below horizontal, when it was at a height of 77.9 km. Fortunately the meteor exploded high in the atmosphere, where most of its energy was dissipated.
(a) Had the meteor not exploded, and ignoring air resistance, how long would it have taken for the meteor to hit the ground from its 77.9-km height?
(b) With the same assumptions as in part (a), how far in horizontal distance would the meteor have traveled from its initial location to when it hit the ground?
(c) Just before striking the ground, what would have been the meteor’s total velocity? (You may give your answer in either speed-angle or x,y component form.)
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A person walks into a room that has, on opposite walls, two plane mirrors producing multiple images. Find the distances from the person to the first three images seen in the left-hand mirror, when the person is 11.0 ft from the mirror on the left wall and 14.0 ft from the mirror on the right wall.
| first image | ft |
| second image | ft |
| third image | ft |
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A father (weight W = 849 N) and his daughter (weight W = 394 N) are spending the day at the lake. They are each sitting on a beach ball that is just submerged beneath the water (see the figure). Ignoring the weight of the air in each ball, and the volumes of their legs that are under the water, find (a) the radius of father's ball and (b) the radius of daughter's ball.
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A set of crash tests consists of running a test car moving at a speed of 12.6 m/s (27.7 m/h) into a solid wall. Strapped securely in an advanced seat belt system, a 63.0 kg (138.6 lbs) dummy is found to move a distance of 0.720 m from the moment the car touches the wall to the time the car is stopped. Calculate the size of the average force which acts on the dummy during that time.
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The force that acts on the dummy has to do (negative) work on the dummy. It must slow the dummy and stop it. Thus the amount of work equals the kinetic energy of the dummy. From the equation of work done by a force we can calculate that force. Using the direction of motion as positive direction, calculate the average acceleration of the dummy during that time (in g's) (use 1g=9.8 m/s2). |
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Use Newton's second law. What should the sign of the answer be? The dummy is being slowed down, so the acceleration is - since the dummy is moving in the + direction. In a different car, the distance the dummy moves while being stopped is reduced from 0.720 m to 0.210 m calculate the average force on the dummy as that car stops. |
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what is mass?
ive done a course on nuclear physics i could tell you lots of things about quarks and draw feinman diagrams but i feel i should really have learned the answer to the question what is mass.
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Most geologists believe that the dinosaurs became extinct 65 million years ago when a large comet or asteroid struck the earth, throwing up so much dust that the sun was blocked out for a period of many months. Suppose an asteroid with a diameter of 2.0 km and a mass of 1.0 ×1013 kg hits the earth (6.0×1024 kg) with an impact speed of 4.2 ×104 m/s.
Part A) What is the earth’s recoil speed after such a collision? (Use a reference frame in which the earth was initially at rest.)
Part B) What percentage is this of the earth’s speed around the sun? The earth orbits the sun at a distance of 1.5×1011 m.
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1. In a simple harmonic motion, the kinetic energy is equal to the elastic potential energy in the position:
a) X = A / 2
b) X = A
c) X = A / (2) 1/2
d) X = (2 ) 1/2 A
e) X = 0
1.2 The displacement of a particle in a simple harmonic motion is given by: X = 10 cos (20t - π / 3), which of the following. expressions is equivalent:
a) X = 10 cos (20t + π / 3)
b) X = 10 sen (20t - 5π / 6)
c) X = 10 sen (20 t + π / 6)
d) X = 10 cos (20 t + 2π / 3)
Thank you!
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A chain pulls tangentially on a 47.5 kg uniform cylindrical gear with a tension of 75.1 N. The chain is attached along the outside radius of the gear at 0.864 m from the axis of rotation. Starting from rest, the gear takes 2.62 s to reach its rotational speed of 1.38 rev/s. What is the total frictional torque opposing the rotation of the gear?
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