Can someone please help me quick :(
A toy spring with a spring constant of 6.4 N/m has a relaxed length of 20.0 cm. When a ball is attached to the end of the spring and allowed to come to rest, the vertical length of the spring is 75.0 cm. What is the elastic potential energy stored in the spring

PE = 0.968  J

Explanation:

the formula for potential elastic energy is

PE = kx^2/2

k = spring constant 6.4 N/m

x = displacement = 75 - 20 = 55 cm = 0.55m

plug these values into the equation

PE = 6.4(0.55)^2 / 2

PE = 0.968  J

d eras and periods

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