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SCI 3700 Developments in the Physical Sciences

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All questions: short answers

Motion

1. A car travels 50 meters east in 15 seconds. What is the car's average velocity?

2. A motorcycle starts from a standstill. In 15 seconds it reaches a velocity of 20 m/s. What is the motorcycle's average acceleration?

3. During the U.S. trials for the 2004 Summer Olympics, Michael Phelps broke his own world record in the 400 meter individual medley when he was clocked at 4:08:41. What was his average velocity and his average speed?

4. Sitting in the passenger seat you observe that the drive of the car needs only 3 seconds to come from a speed of 35 mph on the entrance ramp to the interstate to a speed of 70 mph on the interstate. What is the car's acceleration? How much distance does the car cover during those 3 seconds?

5. Polar bears are strong swimmers and can swim as long as 10 hours without rest. If a polar bear swims with an average speed of 2.6 m/s, what is the total distance it can swim in 10.0 hours? Give your answer in kilometers.

6. How long does it take a baseball to travel the 18.4 m from the pitcher's mound to home plate when thrown at a speed of 34.5 m/s?

7. An airplane starts at rest at the end of a runway. If it reaches a speed of 80 m/s in 18 s, what is the plane's acceleration?

8. If a race car at rest (not moving) accelerates to a speed of 120 m/s in 32s. What is the car's acceleration?

9. You drop a rock from the top of a tall cliff. After 1.50 seconds the velocity of the rock is measured to be 14.7 m/s in a downward direction. What is the rock's acceleration? What would its instantaneous velocity be in another 0.50s?

10. A motorcycle starts with velocity of 10 m/s then accelerates for 40 m/s2 for 2.0 seconds. What is its final velocity?

11. A projectile accelerates from 0 to 280 m/s in 0.5 seconds. What is its acceleration?

12. How long will it take an object with an average velocity of 45 m/s to travel 825 m?

13. Two cars have the same engine and wheels. It is determined experimentally that both cars produce the same force over a 100 meter course. Car A can accelerate twice as fast as Car B. Explain this result using Newton's Second Law.

14. Michele kicks a 0.75 kg ball with a 45 N force. What is the acceleration of the ball?

Work

Q1. Assume that a horse pulls a sleigh in a way that the sleigh moves at constant velocity. What is the work being done on the sleigh (a) by the horse, (b) by the Earth, and (c) by the force of friction? Determine whether the work is positive, zero, or negative.

Q2. Compare the two different scenarios of getting a heavy bag of cement to a height of 1 meter.

(a) Lifting the bag vertically upwards.

(b) Walking up a long ramp to get the bag up to a height of 1 meter.

What is the work done by gravity in either scenario? What is your work done in either scenario? Why do people use long ramps?

Q3. Compare the two different scenarios of getting a heavy piece of furniture up five steps to the main entrance door of a house.

(a) Lifting the heavy piece of furniture and carrying it up the five steps.

(b) Using a long ramp to push the heavy piece of furniture up to the main entrance door of a house.

What is the work done by gravity in either scenario? What is your work done in either scenario? Is there any other work involved?

Work part 2

Q4. A man takes his dog out for a walk. During the walk the dog sees a cat and gives chase. The dog pulls the man 26 meters down the street, exerting a force of 200 newtons. How much work did the dog do?

Q5. You take your new television out of it's box (which is on the floor) and lift it onto a table. The television weighs 15 kg and you did 117.6 joules of work. How high is the table?

Q6. A woman does 27 joules of work pushing a chair 3 meters. How much force did she push with?

Q7. A girl pulling her sled with 12 newtons of force does 540 joules of work. How far did she pull the sled?

Q8. John lifts his book bag 0.9 meters. The book bag weighs 98 newtons. How much work did John do?

Q9. How much force does someone apply doing 90 joules of work to lifting a bag of dog food 1.5 meters?

Q10. How much force is required to lift a potted plant 0.6 meters if the work done was 30 joules?

Q11. You do 1080 joules of work dragging a full trash can with 60 newtons of force. How far did you drag the trash can?

Q12. A shopper pushes a cart with 20 newtons of force for 30 meters. How much work did the shopper do?

Q13. A 1000 kg rock is sitting on a ledge that is 18 meters high. How much potential energy does the rock have?

Q14. How much gravitational potential energy does a 860 kg car at the top of a 32 meter hill have?

Energy

Q3. Unless you push a pendulum at the start of its swing (doing work to give it extra energy), will it ever swing higher than its starting point? Explain your answer in terms of kinetic and potential energy.

Q4. Does a pendulum swing forever? Why or why not?

Q5. Describe the transformations between potential and kinetic energy when you drop a 15000 gram television from a height of 0.8 meters.

Q6. A car with a mass of 860 kg sits at the top of a 32 meter high hill. Describe the transformations between potential and kinetic energy that occur when the car rolls to the bottom of the hill and continues rolling.

Q7. How is the previous problem different from ones where the object comes to a stop at the end of moving/falling? Discuss what happens to the energy in each case and how they are different.

Q8. Describe the transformations between potential and kinetic energy that occur when a 1000 kg rock falls from the top of a 18 meter cliff.

Q9. How much kinetic energy does a 2000 gram ball have the instant before it hits the ground after falling from a height of 6 meters?

Q10. Assume the collision in problem #9 is perfectly elastic (no energy is lost) and there is no air resistance (friction). How high should the ball bounce? Describe the transformations between potential and kinetic energy that will occur from when the ball is dropped until it reaches the top of its first bounce.

Sound Waves

Q1. Explain in your own words what transverse waves are. Include examples.

Q2. Explain in your own words what longitudinal waves are. Include examples.

Q3. In outer space you could see a distant explosion (separated by space), however you would not hear the explosion. Explain why this happens based upon your knowledge of wave propagation.

Q4. Describe the meaning of the following quantities and include in which unit the respective quantity is measured: wavelength, frequency, period, displacement, and wave speed.

Q5. What is the relationship between wavelength and frequency of a wave?

Q6. Find at least two other musical instruments, other than a flute and thumb piano, that are based upon standing waves on strings with both ends fixed and describe them in your own words.

Q7. Find at least two other musical instruments that are based upon standing waves with both ends open and describe them in your own words.

Q8. Find at least two other musical instruments that are based upon standing waves with one end fixed and one end open and describe them in your own words.

Q11. Find out what the frequency of the musical note A4 is and report your finding here. What is the frequency of the musical note A3?

Q12. The speed of sound in air is about 343 m/s. Convert this into miles per hour and into kilometers per hour.

Q13. Calculate the wavelength of the musical note A4 using your answer from Q10 and a speed of sound in air of 343 m/s.

Q14. The length of a guitar's strings is 650 mm. What is therefore the wavelength of a wave on any of the strings if the string is free to move?

Q15. Using your answers from Q11 and Q14, calculate the wave speed on the A4 string of a guitar. What is the wave speed on the A3 string of a guitar?

Q16. You hear your brother playing the guitar in his room at the end of the hall way, 8 m away from you. How long does the sound take to travel from his guitar to your ear?

Q17. Does the amplitude of a wave change its frequency?

Q18. What is the speed of sound in sea water? Whales and dolphins use sound to communicate under water. What are the frequency and the wavelength of the musical note A5 in sea water.

Q19. Find out what ultra-sound is. What are applications of ultra-sound?

Light

Q1. What is the difference between specular and diffuse reflection? Please, use your own words!

Q2. How big is the angle of reflection when compared with the angle of incidence?

Q3. Describe refraction in your own words.

Q4. How big is the angle of refraction when compared with the angle of incidence?

Q5. What is the index of refraction in water? What is the speed of light in water?

Q6. Find out what the distance between the Sun and the Earth is. Calculate from this distance and the speed of light how long it takes the light to travel from the Sun to come to the Earth.

Q7. Find at least 5 types of waves in the electromagnetic wave spectrum and order them by their wavelengths. Include a description of the usage of each of these waves.

Q8. Explain in your own words what the differences between reflection, refraction, and diffraction are.

Q9. Explain for each of the following whether reflection, refraction, and/or diffraction are the principles behind the object or phenomenon:

a.) Eye glasses

b.) rainbow

c.) colors on a CD or DVD

d.) mirror

e.) magnifying glass.

Q10. What are the waves called that have wavelengths just beyond the visible light spectrum? What are they used for?

Q11. You attend a concert and have a seat that is 70 m away from the stage where the sound is produced. How long does it take for the sound to reach your ears? You take a picture with your phone and send it to your friend who could not come to the concert. She lives in a town 45 miles away. How long does it take until she gets the picture on her phone? Please, include the assumptions that you make.

Q12. Why do you think the Doppler Effect is called a red-shift or a blue-shift when it affects light?

Q13. Find out how night-vision equipment works - report your findings and sources here.

Q14. Find out what fiber optics is and state it here.

Sound and light

Q19. Describe the concepts of reflection, refraction, interference, and standing wave

Q20. Describe the differences and similarities between sound waves and light waves using the speed of the waves, their wavelengths, their frequencies, and whether or not the waves need matter to propagate.

Fission/fusion

Q1. Explain what an isotope is. Three known isotopes of hydrogen have the common names hydrogen, deuterium, and tritium. What is the difference between these three isotopes?

Q2. In your own words explain where radiation comes from.

Q3. How many isotopes of carbon are known? Of these how many are stable and how many are unstable? Identify the stable isotopes of carbon.

Q4. Define transmutation. Which type of nuclear reaction is not a transmutation reaction?

Q5. Remember that protons (p^{+}) are positively charged and neutrons (n) are neutral. What fundamental force makes the protons repel each other and what distance does it operate over? What fundamental force holds the protons together and what distance does it operate over?

Q6. Define chain reaction and critical mass as it pertains to nuclear fission.

Q7. For each of the parts of this question, identify the nuclear reaction occurring.

- Light nuclei (such as hydrogen) under high temperature combine to form a larger single nucleus (such as helium).
- An atom of one element is converted to an atom of another element. An example of this is when a spontaneous emission of a beta particle causes a atom of lead-214 to change into bismuth-214.
- A heavy nucleus (such as the U-235 nucleus) splits into two or more parts.

Q10. Look at how radioisotope treatment is used to diagnose and treat hyperthyroidism. In your answer to this question explain what hyperthyroidism is, how (and which) radioisotopes are used to diagnose and treat it, and the benefits and possible drawbacks to this treatment.