Well depending on what current the heater pulls im going to assume about 13, and 13A for the hair dryer, thats 26A on the 40A circuit.
I dont see how a lightbulb could overload the circuit.
Anyway, assuming the circuit is overloaded by some really big heater- the circuit would trip, the fuse would go and remain off. Most houses are fitted with seperate circuits for lights and sockets, so the light may remain on depending on the breaker board. - the reason for them all being able to run with the sudden overload may be due to a surge.
One solution to this is not to put such a large heater on the circuit with other appliances.
Another may be to dry your hair in the dark
Not sure if this it completely right but here’s what I got: 77.16050617284 J
Answer:
F = 326.7 N
Explanation:
given data
mass m = 200 kg
distance d = 2 m
length L = 12 m
solution
we know force exerted by the weight of the rock that is
W = m × g ..............1
W = 200 × 9.8
W = 1960 N
and
equilibrium the sum of the moment about that is
∑Mf = F(cos∅) L - W (cos∅) d = 0
here ∅ is very small so cos∅ L = L and cos∅ d = D
so F × L - W × d = 0 .................2
put here value
F × 12 - 1960 × 2 = 0
solve it we get
F = 326.7 N
To solve this problem we will apply the concepts related to energy conservation. So that the initial energy on the system is equivalent to the final energy.
The initial or final energy will also be the TOTAL mechanical energy of the body.
In the case of the initial energy we will have two types of energy on the body: Kinetic energy and potential energy.
For the case of the final energy we will only have the potential energy in terms of the height 
, the mass m, and the gravity g
The total mechanical energy will be equivalent in the terms required, to the final potential energy.
