Physics homework help

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Note: Throughout this  use g = -10 m/s^2 for the gravitational acceleration of the earth. Ignore air resistance or friction between surfaces.

1. Briefly explain the following terms:

(1) Newton’s three laws of motion

(2) Potential energy and Kinetic energy

(3) Conservation of momentum

(4) Absolute temperature

(5) First and Second law of thermodynamics

2. Suppose a car was at rest and then started accelerating at constant rate of 10 m/s2. What is the car’s velocity after 20 seconds? How far has it travelled during that time?

3. A stone is thrown straight up with the initial velocity of 50 m/s. Calculate the position and velocity of the stone at t = 1 sec, 2 sec and 3 sec after it is thrown. (Section 2.7)

4. A baseball is thrown at angle of 45o above the horizontal with initial speed of  m/s.

(1) How far has it travelled horizontally when it is at the highest position?

(2) How long does it take for the ball to reach the highest position? (Section 3.4)

5. A child is riding a merry-go-round that is rotating at 10.0 rev/min. How much is the centripetal force exerted on her if her mass is 20 kg and she is 2 m from the center? (Section 6.3)

6. A planet has mass 3.0 × 1023 kg and radius 2.0 × 106 m. Calculate its acceleration of gravity. Use G = 6.67 × 10-11 N kg-2 m2.

7. A ball of mass 3 kg was moving at constant velocity 5 m/s before colliding a second ball at rest whose mass is 4 kg. After the collision, the first ball moves at 2 m/s to the same direction as the initial movement. Assuming the collision was elastic, calculate the velocity of the second ball.

(Section 8.4)

8. A skater was rotating at 0.8 rev/s with her arms extended, and is rotating at 4 rev/s when she pulls in her arms. Her moment of inertia was 2.5 kg m2 when her arms were extended. What is her moment of inertia when she pulled in her arms? (Section 10.5)

9. At which temperature will the average kinetic energy of gas molecules be twice as much as that at temperature 0oC? Answer in Celsius.

10. A Carnot engine operates between temperatures 400oC and 20oC. What is its theoretical maximum efficiency? (Section 15.4)

11. A particular microwave has frequency 15 GHz (that is, 1.5 x 1010 vibrations per second). Using the speed of light c = 3.0 x 108 m/s, Calculate its wavelength. (Section 16.9)

12. Explain why free charges in static distribution inside conductors are located at the surface. (Section 18.7)