# Project #69853 - Physics Concepts and Questions

1.What is meant by rotational imbalance? Under what circumstances does it arise?

2. What is the connection between work and kinetic energy?

3. Explain how the acceleration of an object moving in a circle can be broken up into radial and tangential components. What does each tell you about the particular motion?

4. Explain why you cannot have a geosynchronous satellite directly over yourself?

5. What is potential energy? How is it defined Mathematically? How does it relate to work?

6. What is meant by the "normal" force? How does one find the normal force on an object in a given situation?

7. If you throw a rock up in the air, with negligible air resistance, compare its acceleration at the top of its flight with its acceleration just after it leaves your hand and its acceleration just before it his the ground.

8. Explain what is meant by centripetal acceleration.

9. Compare and contrast "unit" and "dimension". Give an example of each.

10. Explain how to compare velocities as measured in two different frames of reference, one of which is moving relative to the other.

Problems:

1. The take-off speed (no wind) of an Aeronca Champ is 80km/h. The pilot takes off from the runway that is 145m long, just long enough for the plane to reach take-off speed right at the end of the runway. What must be the acceleration of the airplane? Assume that it starts from rest and the acceleration is constant.

2. Consider the following two vectors, A = 4.0i+3.2j-7.5k , B=1.8i-9.7j+3.5k
, Express the following in unit-vector notation: -2A + 3B

3. A beaver slaps its tail on the water and a particular drop of water is projected vertically with an initial speed of 18.3m/s. How high does the drop of water go? Assume no air resistance.

4. A 20.5 kg beaver pushes a 10.7kg log through the water. The water exerts a 20.7N drag force (Opposite the motion) on the log and a 5.25N drag force (opposite the motion) on the beaver. If the beaver and log both speed up together with an acceleration of 1.37m/s^2, what must be the force of contact between the beaver's nose and the log? Assume the beaver and log are moving horizontally only.

5. A ball launches itself into the air from level ground with a speed of 3.25m/s, at an angle of 37 degrees with the horizontal. How far away does the ball land?

6. The cruising speed of a swimmer is 4.2miles/hour. How many seconds would it take a swimmer to swim the length of the lake (4.5523 x 10^6 cm). You may want to know that there are 2.54 cm in on inch.

7. A tree falls rotating about its base, a nut located 13m from the point of rotation is, at one point, traveling 5.32m/s. What is the centripetal acceleration of the hickory nut at that point in time?

8. Find the magnitude and direction of the vector C (C and theta), given that A+B+C = -.486i+.417j. (A=1.5 cm up y axis, B=2 cm across X, Btheta=25 degrees)

9.Person checks out one of the water slides, which makes an angle of 37 degrees with horizontal. If the coefficient of kinetic friction between the slide and the persons butt is .095 What is the acceleration of the person while sliding down the slide? What is the acceleration of the person while sliding up the slide, having been given an initial upward velocity?

10. Given that the mass of Earth is 5.97 x 10^24 kg and the radius is 6.38 x 10^3, calculate the force of gravity on a 27.2kg animal orbiting 1,850km above the Earth's surface. Also calculate the period of the animal's orbit.

11. The animal from problem 10, is in the astronaut program, rides in a flight simulator that axts like a ferris wheel, moving in a verticle circle of radius 5m. If it rotates at constant velocity so as to make on revolution every 3.25 seconds, what is the magnitude and direction of the force exerted on the beaver by the centrifuge at the movent the animal is at the top of the circular path? At the bottom of the circular path? Assume Earth's gravity.

12. You push a 30.3kg piano up a ramp inclined 43.7 degrees with horizontal. What is the work done by your applied force if you push the piano a total distance of 45.7 m and the coefficient of kinetic friction between the ramp and piano is .273? Assume you push the piano up the incline at a constant speed, and that your applied force parallel to the ramp.

13. How much total work is required to stop a 27.2kg person that is moving at a speed of 375m/s?

14. A 3.25 kg mass baby is attached to a spring, and oscillates back and forth on a frictionless horizontal surface. If the spring (with spring constant 37N/m) is stretched a distance of .237 m from equilibrium and then released from rest, calculate: The total mechanical energy? The potential energy when it is at a distance .175 m from equilibrium? The kinetic energy when it is at a distance .175 m from equilibrium?

15. While playing ping pong, a person spikes the ball and it hits the table at an angle of 77.5 degrees to the normal and with an initial speed of 21.7m/s. If it bounces off at the same angle with the normal, but with a speed of 18.5m/s, what impulse does the table impart to the ball? Assume the ball has a mass of 7.75 grams.

16. A 27.5 beaver, swimming westward at 3.25m/s, collides head-on with a 18.2kg beaver initially swimming eastward at 5.75m/s. If the two beavers stick together, what is their velocity immediately after the collision? Assume external force of drag from the water is negligible during the short duration of the collision.

17. While rotating about his center of mass, the angular velocity of a cylinder changes from 2.25 rad/s to 1.15 rad/s in 18.3 seconds. What must be the net torque acting on the cylinder? Assume that the cylinder is a uniform, solid cylinder of mass 27.5 kg, radius .235m, and height .75 m.

18. A tire of mass 27.5 kg rolls without slipping with its center of mass travelling at a constand speed of 2.5m/s. Calculate the total kinetic energy of the rolling tire, assuming it is a thin, hollow spherical shell of radius .475m.

19. A thin rod of mass 1.37kg and length .75m is pivoted at its center, initially at rest in a verticle position. A small blob of pond mud, mass of .275kg and traveling horizontally at 3.75m/s, strikes the rod at its bottom end and sticks there. What is the angular velocity of the rod immediately after the mud sticks to it?

20. A horizontal diving board of mass 18kg and length 2.5m sits on two verticle support posts that are .5 m apart, with one of the posts being located at left-hand end of the diving board. A 1.15 tall, 27.5 kg person stands at the opposite end of the diving board (the end with no support posts under it). What are the magnitudes and directions (up or down) of the forces exerted on the board by each of the two support posts? Assume the board does not flex.

21. Find the center of mass for the table in the file below. Assume it is a flat, 2 demensional table, with uniform density throughout, and a uniform thickness of 1.55 inches.

Continuations of Concepts (5 is missing otherwise everything is on file)

5. Show the relation between the speed of transverse wave on a string and the properties of the string. Explain what is meant by interference of waves. What is the principle of superposition? Describe, qualitatively and quantitatively, what happens when two waves interfere that have the same amplitude, frequency, and wavelength, but that have different phase constants. What is the result? What is meant by constructive interference? What is meant by destructive interference?

 Subject Science Due By (Pacific Time) 05/16/2015 12:00 am
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