Answer: 17.5N
Step-by-step explanation:
Given that,
spring constant (k) = 70N/m
Original length (lo) = 40 cm
New length (ln) = 15 cm
extension of spring (e) = new length - original length
i.e e = ln - lo
e = 15 cm - 40 cm
e = -25cm (the negative sign is negligible, just the same magnitude matters)
So, convert 25cm to metres
If 100cm = 1m
25cm = 25/100 = 0.25m
(Note that how hard the spring push refers to the Force, hence, find force.)
Now, apply the Hooke law (F = ke)
Force = spring constant x extension
F = 70N/m x 0.25m
F = 17.5N
Thus, the spring push with a force of 17.5N when compressed.