Answer:
k1 + k2
Explanation:
Spring 1 has spring constant k1
Spring 2 has spring constant k2
After being applied by the same force, it is clearly mentioned that spring are extended by the same amount i.e. extension of spring 1 is equal to extension of spring 2.
x1 = x2
Since the force exerted to each spring might be different, let's assume F1 for spring 1 and F2 for spring 2. Hence the equations of spring constant for both springs are
k1 = F1/x -> F1 =k1*x
k2 = F2/x -> F2 =k2*x
While F = F1 + F2
Substitute equation of F1 and F2 into the equation of sum of forces
F = F1 + F2
F = k1*x + k2*x
= x(k1 + k2)
Note that this is applicable because both spring have the same extension of x (I repeat, EXTENTION, not length of the spring)
Considering the general equation of spring forces (Hooke's Law) F = kx,
The effective spring constant for the system is k1 + k2
scientific notation is given as

here we know that
1 < a < 10 and
k = whole number
now the number will be
N = 299,790,000
here we know that

so we have
a = 2.99
k = 8
To lift the bag straight up takes (F · D) = (45 · 1.2) = 54 joules of energy (work).
Moving the bag horizontally 'across' gravity requires no work.
It doesn't matter how far.
False because friction will generate heat energy and/or sound energy etc. Think of a car stopping or a broom sweeping the ground.