Question

If I want the spring to stretch to $11$ cm long, how much weight should I put on?

• A. $4.5$ kg
• B. $5$ kg
• C. $4$ kg
• D. None of these

Answer 1

The correct option is C $4$ kg

$F=kx$, is the equation of the spring force, where $x$ is the displacement in the spring.
$k=\frac{F}{x}$
$k=\frac{mg}{x}$
$k$ is the slope of weight vs stretch in the spring.
$slope=\frac{2-1}{8-6.5}=\frac{1}{1.5}=0.67$
$F=0.67\left(11\right)=4kg$