U6 Videos FP 5.3.2

When a mass is suspended vertically from a spring and is at rest, which forces are acting on the mass?

• Force of gravity, applied force, normal force, and spring force.

• Force of gravity and applied force.

• Force of gravity and spring force.

• Normal force and spring force.

In Hooke's Law, F_s = -kx, what does the negative sign indicate?

• The spring constant is always negative.

• The force of the spring is always directed downwards.

• The force of the spring is opposite to the direction of the spring's displacement.

• The spring is losing energy.

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When applying Hooke's Law (F_s = kx) in Newton's Second Law for a vertically hanging spring at rest, why is the magnitude of the displacement (x) used instead of its vector value (which would be negative if downward)?

• The spring constant (k) is always positive, so x must also be positive.

• The direction of the spring force has already been accounted for in the free body diagram and the sum of forces equation.

• The negative sign in Hooke's Law only applies to horizontal springs.

• The displacement is always considered positive in physics problems.

A spring has a natural length of 5.4 cm. When a 25-gram mass is suspended from it, the spring extends to a length of 11.4 cm. What is the spring constant of the spring?

• 2.0 N/m

• 4.1 N/m

• 8.2 N/m

• 16.4 N/m