Critical Thinking
Calculating A small meteoroid is approaching Earth. It has a mass of 100.0 kg and a speed of 10.0 km/s. How much kinetic energy does the meteoroid have? (Hint: 1 km = 1000 m)
Designing an Experiment Design an experiment to find out how much elastic potential energy is in a compressed spring. In addition to the spring, you may use a small metal ball, a ruler, and a scale for measuring mass.
Calculating A 0.15-kg ball is dropped from the top of a 150-m building. What is the kinetic energy of the ball when it passes the sixteenth floor at a height of 63 m? (Ignore air resistance.)
Math Skills
Converting Units Using mass in kg, velocity in m/s, and height in m, show that the formulas for kinetic energy and gravitational potential energy result in energy values with the same units. What is the energy unit called?
Questions 27—29 refer to the data in the table below.
Three balls are thrown vertically into the air from different heights above the ground. The data for each ball are shown in the table below.
Data Table |
|||
|---|---|---|---|
Object |
Mass (kg) |
Initial Upward Speed (m/s) |
Initial Height Above Ground (m) |
Ball 1 |
1.00 |
8.00 |
15.00 |
Ball 2 |
2.00 |
1.00 |
10.00 |
Ball 3 |
3.00 |
4.00 |
5.00 |
Calculating How much kinetic energy does each ball have when it is thrown?
Analyzing Data Which ball has the greatest gravitational potential energy when it reaches its maximum height? (Hint: Find the total energy for each ball.)
Predicting Which ball hits the ground with the most kinetic energy?
Concepts in Action
Using Graphs A soccer ball is kicked from the ground into the air. Describe two graphs that show how the potential energy and kinetic energy change between the time the ball is kicked and when it lands. (Hint: Make time the x-axis.)
Inferring When a falling object reaches a speed called terminal velocity, its speed no longer increases. The object is losing gravitational potential energy but not gaining kinetic energy. Since energy must be conserved, where must the gravitational potential energy be going?
Calculating Suppose a 200.0-kilogram dolphin is lifted in the air to be placed into an aquarium tank. How much energy is needed to lift the dolphin 3.00 meters into the air?
Applying Concepts How is energy converted as a car moves between the top and the bottom of a roller coaster loop?
Making Judgments What are some advantages and disadvantages of solar energy?
Applying Concepts How can electricity be obtained from the wind?
Writing in Science Using your own words, write a brief summary of the law of conservation of energy. Include an example from your everyday life.
Performance-Based Assessment
Applying Concepts Identify one practical way that your family or school could reduce energy use. Find out how much energy is currently being used for the purpose you choose, and estimate how much energy your suggestion could save. Write a brief summary of your recommendations.
Table of Contents