B) The amount of work done
Incomplete question. Missing part:
"it took him 10 seconds to move the couch. What was his power?"
Answer:
50 W
Explanation:
The power developed is given by:

where
W is the work done
t is the time taken
In this problem,
W = 500 J
t = 10.0 s
Substituting into the equation, we find

Answer:
8.8 × 10⁻³ g/L
Explanation:
NaF is a strong electrolyte that ionizes according to the following reaction.
NaF(aq) → Na⁺(aq) + F⁻(aq)
Then, the concentration of F⁻ will also be 0.10 M.
In order to find the solubility of PbF₂ (S), we will use an ICE Chart.
PbF₂(s) ⇄ Pb²⁺(aq) + 2 F⁻(aq)
I 0 0.10
C +S +2S
E S 0.10 + 2S
The solubility product (Kps) is:
Kps = 3.6 × 10⁻⁸ = [Pb²⁺].[F⁻]² = S . (0.10 + 2S)²
In the term 0.10 + 2S, 2S is negligible in comparison with 0.10 and we can omit it to simplify calculations.
Kps = 3.6 × 10⁻⁸ = S . (0.10)²
S = 3.6 × 10⁻⁵ M
The molar mass of PbF₂ is 245.20 g/mol. The solubility of PbF₂ in g/L is:
3.6 × 10⁻⁵ mol/L × 245.20 g/mol = 8.8 × 10⁻³ g/L
Dna is the way to answer this questions
Explanation:
Given that,
Mass of the rock climber, m = 90 kg
Original length of the rock, L = 16 m
Diameter of the rope, d = 7.8 mm
Stretched length of the rope, 
(a) The change in length per unit original length is called strain. So,

(b) The force acting per unit area is called stress.

(c) The ratio of stress to the strain is called Young's modulus. So,

Hence, this is the required solution.