Answer:
16 J
Explanation:
It is given that,
Work done, W = 2 J
A spring is stretched by 2.0 cm from its equilibrium length
We need to find how much more work will be required to stretch it an additional 4.0 cm.
Let k is the spring constant of the spring. When W = 2J, and x = 2 cm, then energy required to stretch the spring is :

The energy required to stretch the spring from 2 cm to additional 4 cm i.e. 2+4= 6 cm.

So, the required work done is 16 J.
B. picking up a box off the floor
Answer:
0.5 Ohms
Explanation:
We note that the node Q is also between the resistors of 1ohm and 2ohms.
We note that the node P is also between the resistors of 2ohms and 3ohms.
Thus, all these resistors are in parallel, beween nodes P and Q
1/Re=1/R1+1/R2+1/R3
1/Re=1/1+1/2+1/3=(6+3+2)/6=11/6 [ohm^(-1)]
Re=6/11=0.54ohms
Rounding to the tenth: Re=0.5 ohms