GRADE 9 SCIENCE · CHAPTER 3
Forces, energy & waves
Study each lesson in order, or choose the idea you need today.
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Energy systems
Account for useful and transferred energy
Use a stated system boundary to calculate efficiency and account for energy transferred to other forms.
AN EXAMPLE FROM THIS CHAPTER
A motor receives 100 J and transfers 40 J to useful lifting. What is its efficiency for lifting?
Show answer & explanation
40%
40 ÷ 100 × 100% = 40%.
Curriculum & source notes
These are original Little Play study books organized around U.S. school topics. The official curriculum references below guide topic scope and progression. Coverage is selected, not a complete curriculum or a verified match to every state standard. They are not copies of a publisher’s textbook. Check your school’s syllabus and book edition.
High-school courses can be taken in different years. Choose the topic that matches the student’s current course.
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