Which one of the following statements is true concerning the motion of an ideal projectile launched at an angle of 45°to the horizontal（）
A. The acceleration vector points opposite to the velocity vector on the way up and in the same direction as the velocity vector on the way down
B. The speed at the top of the trajectory is zero
C. The object’s total speed remains constant during the entire flight
D. The horizontal speed decreases on the way up and increases on the way down
E. The vertical speed decreases on the way up and increases on the way down
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The radial component of velocity for a particle moving in a circular path is____（）
A non-zero constant
B. Radius itself
C. Variable
D. Zero
Which of the following is a scalar quantity（）
A. speed
B. time
C. length
D. instantaneous acceleration
E. instantaneous velocity
F. average velocity
G. average acceleration
H. magnitude of position vector
I. none of the above
In the processing of pasteurized milk, the minimum processing is to destroy（）
A. Clostridium botulinum
B. pathogens such as salmonella, mycobacterium tuberculosis
C. enzymes
D. molds
Which statement about values is incorrect（）
A. Values are social principles, goals, or standards accepted by persons in a culture
B. Values are learned by contacts with family members, teachers, and religious leaders
C. Values will be influenced by what is seen on television or read in newspapers
D. People in various cultures have basically similar values
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