What is the half-life of Ra-226?

Introductory Chemistry 5
What are the basic unitssingle atoms, molecules, or formula unitsthat compose each substance? (a) \(\mathrm{Rb}_{2} \mathrm{O}\) (b) \(\mathrm{N}_{2}\) (c) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) (d) \(\mathrm{~N}_{2} \mathrm{~F}_{4}\)

Classical Mechanics 0
Consider an object that is coasting horizontally (positive x direction) subject to a drag force f = by cv2. Write down Newton's second law for this object and solve for v by separating variables. Sketch the behavior of v as a function of t. Explain the time dependence for t large. (Which force term i

Campbell Biology 9
A controlled experiment is one that a. proceeds slowly enough that a scientist can make careful records of the results. b. tests experimental and control groups in parallel. c. is repeated many times to make sure the results are accurate. d. keeps all variables constant. e. is supervised by an experi

Probability and Statistics 4
Suppose that a failure in a certain electronic system can occur because of either a minor or a major defect. Suppose also that 80 percent of the failures are caused by minor defects, and 20 percent of the failures are caused by major defects. When a failure occurs, n independent soundings X1,...,Xn a

Campbell Biology: Concepts & Connections 7
Neurons communicate at synapses. The transmission of signals between neurons or between neurons and effector cells occurs at junctions called synapses. At electrical synapses, electrical signals pass directly between cells. At chemical synapses, the sending (presynaptic) cell secretes a chemical sign

Inquiry into Physics 7
A 0.1-kg ball is attached to a string and whirled around in a circle overhead. The string breaks if the force on it exceeds 60 N. What is the maximum speed the ball can have when the radius of the circle is 1 m?

Life-Span Human Development 9
Distinguish between concrete operational thinking and formal operational thinking in terms of what is operated upon mentally, using specific examples if you can.

Biology for AP Courses
The secretion of hormones by the pituitary gland is an example of which type of signaling? a. autocrine signaling b. direct signaling across gap junctions c. endocrine signaling d. paracrine signaling