The average adult in the us spends 24 hours watching televistion each week
Answer:
Explanation:
Starting from the equation:
First of all, let's multiply by t on both sides:
And then, let's divide by v on both sides:
So, finally
Answer: Current = 2 A
Explanation:
Given that an electrical power plant generates electricity with a
current I = 50 A
Potential difference V = 20 000 V
The resistance R will be achieved by Ohms law formula which state that
V = IR
But the power generated will be the product of potential difference and the current
Power P = IV
P = 50 × 20000
P = 1, 000000 W
When the transformer steps up the potential difference to 500 000 V before it is transmitted
Power is always constant.
Using the formula for power again with
V = 500000
1000000 = 500000× I
Make I the subject of formula
Current I = 1000000/500000
Current I = 2 A
Answer:
The temperature will decrease (get colder).
Explanation:
Enthalpy changes are heat changes accompanying physical and chemical changes. The enthalpy change is the difference between the sum of the heat contents of products and the sum of heat contents of reactants.
- For an endothermic change, heat is absorbed for the reaction.
- The surrounding becomes colder at the end of the reaction and so is the reaction itself.
- The right choice is that the temperature will decrease.
Assume no air resistance, and g = 9.8 m/s².
Let
x = angle that the initial velocity makes with the horizontal.
u = 30 cos(x), horizontal velocity
v = 30 sin(x), vertical launch velocity
The horizontal distance traveled is 55 m, therefore the time of flight is
t = 55/[30 cos(x)] = 1.8333 sec(x) s
With regard to the vertical velocity, and the time of flight,obtain
[30 sin(x)]*(1.8333 sec(x)) + (1/2)*(-9.8)*(1.8333 sec(x))² = 0
55 tan(x) - 16.469 sec²x = 0
55 tan(x) - 16.469[1 + tan²x] = 0
16.469 tan²x - 55 tan(x) + 16.469 = 0
tan²x - 3.3396 tan(x) + 1 = 0
Solve with the quadratic formula.
tan(x) = 0.5[3.3396 +/- √(7.153)] = 3.007 or 0.3326
Therefore
x = 71.6° or x = 18.4°
The time of flight is
t = 1.8333 sec(x) = 5.8096 s or 1.932 s
The initial vertical velocity is
v = 30 sin(x) = 28.467 m/s or 9.468 m/s
The horizontal velocity is
u = 30 cos(x) = 9.467 m/s or 28.469 m/s
If t = 5.8096 s,
u*t = 9.467*5.8096 = 55 m (Correct)
or
u*t = 28.469*15.8096 = 165.4 m (Incorrect)
Therefore, reject x = 18.4°. The correct solution is
t = 5.8096 s
x = 71.6°
u = 9.467 m/s
v = 28.467 m/s
The height from which the ball was thrown is
h = 28.467*5.8096 - 0.5*9.8*5.8096² = -110.4 m
The ball was thrown from a height of 110.4 m
Answer: h = 110.4 m
