A 10-kg mass, hung by an ideal spring, causes the spring to ...

[SO00]

A 10-kg mass, hung by an ideal spring, causes the spring to stretch 2.0 cm. What is the spring constant (force constant) for this spring?
 
  A) 5.0 N/cm
  B) 49 N/cm
  C) 0.20 N/cm
  D) 20 N/m
  E) 0.0020 N/cm

Question 2

The image formed by a single concave lens
 
  A) is always real.
  B) is always virtual.
  C) could be real or virtual, depending on whether the object distance is smaller or greater than the focal length.
  D) could be real or virtual, but is always real when the object is placed at the focal point.
  E) is always inverted.

[Dominic]

Answer to Question 1

B

Answer to Question 2

B

[SO00]

TYSM

[xiaomengxian]

Excellent