Question

1. A student believes that colder water makes fish swim faster. He sets up an experiment using different temperatures of water and measures the speed of the fish. (Chapter 1 – Page 9)
a. What is the independent variable?
b. What is the dependent variable?
c. List two constants the student should have for this experiment.

2. Convert 0.375 mg to grams. Show your work with units in order to receive credit. (Chapter 1 – Page 16)


3. A race car drives one lap around a race track that is 500 meters in length. (Chapter 2 – Pages 45-46)
a. What is the driver’s displacement at the end of the lap?
b. How is his displacement different from the distance traveled?


4. How far does a car travel in 90 seconds if it is traveling at a speed of 55 m/s? Show the appropriate equation from your textbook and show your work with units in order to receive credit. (Chapter 2 – Pages 46-47)


5. Two cars, both with a mass of 500 kg, are traveling down a road. The first car has a velocity of 65 m/s east and the second car has a velocity of 85 m/s west. (Chapter 2 – Pages 54-55)
a. Calculate the momentum of both cars showing the appropriate equation from your textbook and your work with units in order to receive credit.
b. Which car has the larger momentum? Explain how you know.


6. An airplane traveling at 60 m/s comes to a stop in 10 seconds. Calculate the airplane’s acceleration. Show the appropriate formula and show your work with units in order to receive credit. (Chapter 2 – Pages 57-58)


7. An individual has a weight of 735 Newtons. What is the individual’s mass? Show the appropriate equation from your book and show your work with the units in order to receive credit. (Chapter 3 – Pages 78-79)

8. In terms of Newton’s First Law of Motion, explain why it is important to wear a seatbelt while riding in a car. (Chapter 3 – Page 86)


9. If you kick a tennis ball with 50 N of force and then kick a soccer ball with 50 N of force, explain the difference in their motion according to Newton’s Second Law. (Chapter 3 – Pages 81-82)


10. Describe how the velocity and acceleration of a skydiver changes as she falls from the plane back to the ground. (Chapter 3 – Pages 88-89)


11. A child is swinging on swing. Describe what happens to both the kinetic energy and potential energy of the child as she swings up and down. (Chapter 4 – Pages 123)


12. Driving to work one morning, you get a flat tire. When using the car jack, you apply 120 N of force to the jack and the jack in turn applies 2000 N of force to lift the car up. What is the mechanical advantage of the jack? (Chapter 4 – Page 111)


13. A temperature of a 50 kg block increases by 15°C when 337,500 J of thermal energy are added to the block. (Chapter 5 – Pages 141-142)
a. What is the specific heat of the object? Show the appropriate equation from your book and show your work with units.
b. What is the block made of? Use the chart on page 141.
c. Is this block a good material for insulators or conductors?


14. Explain why gases make better thermal insulators than solids or liquids. Give one example from the textbook of a thermal insulator that can help keep you warm on a cold day. (Chapter 5 – Pages 147)


15. Several days after a snowfall, the roofs of some homes on your street have almost no snow on them, while the roofs on other homes are still snow covered. Assuming they have all received the same amount of sunlight, give one reason for this observation related to thermal energy and insulation.


16. If you purchased a string of lights, how could you determine if the lights were wired in series or parallel? (Chapter 6 – Pages 185-186)


17. What happens to the current in a device if the resistance is decreased but the voltage stays the same? (Chapter 6 – Pages 181-182)


18. You measure the voltage difference of a circuit to be 15 V and the resistance to be 675 Ω. What is the current in the circuit? Show the appropriate equation from your book and show your work with units. (Chapter 6 – Page 182)


19. Explain why a magnet from your refrigerator could not be used to lift something as heavy as a car. (Chapter 7 – Pages 202-203)

Answer 1

Answer: (All computations are attached)

1.  Read below for explanation

a. Temperature of water

b. Speed of the fish

c. Fish species and unit of measurement

2. 0.000375 grams

3.

a. 0 meters

b. Distance would be 500m while Displacement would be 0 m. (Read below for explanation)

4. 4,950 meters

5. a. Car 1 = 32,500 kg.m/s ; Car 2 = 42,500 kg.m/s

   b. Car 2. The mass and velocity is directly proportional to momentum. Car 2 has the higher velocity (mass is equal), which means it would have the higher momentum.

6. -6 m/s²

7.  7kg

8. Read below

9. Read below

10. Read below

11. Read below

12. 16.67

13. 450 J/kg/°C

14.Read below

15. Read below

16. Take one bulb off.

17. Read below

18. 0.02 A or 20 mA

19. Read below

Explanation:

1.a.The independent variable is the variable that is changed throughout the experiment to see its effect on what is being tested. In this case, to see whether temperature has effect on the speed of the fish, the temperature needs to vary.

1.b The dependent variable is what is being tested, which in this case is the speed of the fish. It is called as such because change is dependent on the independent variable.

1.c. In an experiment, there are other variables that need to be controlled meaning they are held constant to ensure that no other factors influence the results of the experiment. In this case, the type of fish should be held constant because fishes can have different natural speed depending their species. Another would be the unit of measurement of which the speed is being measured. There are different units of speed and all with different increments. In order to take down accurate data, it must be held constant because even with conversions, the slightest difference can change the result of the data.

3.b. When we talk about distance, we refer to the sum of the distance traveled, or the total distance traveled regardless of direction. When we say displacement, it is the distance with regards to a point of reference. In simpler terms, displacement is the straight path from the starting point to the endpoint. In this case, displacement is zero because the starting point is also the end point. So if we measure the distance between each, then it would be zero because he is back to where he started.

8. Newton's first law of motion is the law of inertia it states that an object at rest will remain at rest and an object in motion will stay in motion with the absence of an unbalanced force. When riding in a car, the car is moving forward, since you are on it, you are moving forward with the car as well. If a car suddenly stops, the brakes is applied to the car, but not to you, which means you would continue to move forward. The seat belt is the brakes that is applied on you. It stops you from moving forward.

9. According to the law of acceleration, the acceleration of an object is directly proportional to the force applied and indirectly proportional to the mass of an object. The formula would be:

$a =\dfrac{F}m$

So in this case, a tennis ball would have less mass than the soccer ball. (The force applied is the same in this scenario). So as the mass increases the acceleration decreases. So the tennis ball would accelerate more than the soccer ball.

10. The gravity of Earth pulls an object towards it continuously at a constant acceleration of 9.8m/s². So when a skydiver jumps out from a certain height, the Earth will pull her down continuously at a rate of 9.8m/s². With each second, her velocity changes. Without any air resistance, the speed will continue to increase.

11. At the highest points of the swing, the child will have its highest potential energy and at the same time, zero kinetic energy. This is because at these two points, the child is at rest. However, as the child swings downwards, its potential energy lessens and kinetic energy increases.

(see attachements for the other explanations)