A perpetual-motion machine can never be built because it is not possible to eliminate...
2 answers:
Answer:
D) Friction
Explanation:
Perpetual Motion machine is that machine which will convert whole input energy into useful work.
So we will say that perpetual motion machine is an hypothetical machine which will be 100% efficient and it will convert whole input energy into useful work without any loss of energy.
we know that efficiency is given as
So in real conditions it is not possible to eliminate frictional force due to which we will not able to get 100% useful work so here in real conditions the efficiency is always less than 100%
so correct answer will be
D) Friction
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Answer:
The object accelerates downward at 4 m/s² since the tension on the rope is less than weight of the object.
Explanation:
Given;
mass of the object, m = 2 kg
weigh of the object, W = 20 N
tension on the rope, T = 12 N
The acceleration of the object is calculated by applying Newton's second law of motion as follows;
T = F + W
T = ma + W
ma = T - W
(the negative sign indicates deceleration of the object)
The object accelerates downward at 4 m/s² since the tension on the rope is less than weight of the object.