A force of 20 N compresses a spring with a spring constant 50 N/m. How much energy is stored in the spring?

4J

Explanation:

Hooke's Law states:

F = -kx

where F = force

k = spring constant

x = displacement of spring

20 = -(50)x

-20/50 = x = -2/5

We can now use this information to find the energy in the Elastic Potential Energy Formula which is...

1/2(k)(x)^2

1/2(50)(2/5)^2 = 4J

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg