Answer:
30 miliAmps
Explanation:
Step 1:
Obtaining an expression to solve the question. This is illustrated below:
From ohm's law,
V = IR
Were:
V is the voltage.
I is the current.
R is resistance.
From the question given, we were told that the resistance is constant. Therefore the above equation can be written as shown below:
V = IR
V/I = constant
V1/I1 = V2/I2
V1 is initial voltage.
V2 final voltage.
I1 is initial current.
I2 final current.
Step 2:
Data obtained from the question. This include the following:
Initial voltage (V1) = V
Initial current (I1) = 60 miliAmps
Final voltage (V2) = one-half of the original voltage = 1/2V = V/2
Final current (I2) =..?
Step 3:
Determination of the new current. This can be obtained as follow:
V1/I1 = V2/I2
V/60 = (V/2) / I2
Cross multiply to express in linear form
V x I2 = V/2 x 60
V x I2 = V x 30
Divide both side by V
I2 = (V x 30)/V
I2 = 30mA.
Therefore, the new current is 30miliAmps
Answer:
72.75 kg m^2
Explanation:
initial angular velocity, ω = 35 rpm
final angular velocity, ω' = 19 rpm
mass of child, m = 15.5 kg
distance from the centre, d = 1.55 m
Let the moment of inertia of the merry go round is I.
Use the concept of conservation of angular momentum
I ω = I' ω'
where I' be the moment of inertia of merry go round and child
I x 35 = ( I + md^2) ω'
I x 35 = ( I + 25.5 x 1.55 x 1.55) x 19
35 I = 19 I + 1164
16 I = 1164
I = 72.75 kg m^2
Thus, the moment of inertia of the merry go round is 72.75 kg m^2.
Answer:
b) vary with the frequency of the light
Explanation:
The phone electric effect can be expressed as
K.E=(hv -W•)
Where K.E is the Kinectic energy
W• = work function of the metal
ν =frequency of the radiation
h = Planck's constat
Then, we can see that K.E is proportional linearly to "v" in the equation above.
Therefore, When light is directed on a metal surface, the kinetic energies of the photoelectrons vary with the frequency of the light
Let us first calculate heat obtained by the evaporation of 51 g of water.
Given, heat of vaporization of water = 2.4 kJ/ g
∴ Heat obtained by evaporation of 51 g of water = 2.4 × 51 = 122.4 kJ
This is the heat energy available that can be used to cool water from 42°C to 20°C.
Specific heat of water is given by,
Here,
C is the specific heat of water = 4.18 J/gK
Q is the amount of heat = 122400 J
m is the mass of the water that can be cooled.
dt is the change in temperature= 42°C ₋ 20°C = 22°C ( The numerical value will be the same if Kelvin unit is used.)
Substituting the values we get,
m = 1331 g
1331 grams of water can be cooled from 42°C to 20°C by evaporation of 51 g of water.
Answer:
False
Explanation:
Gravity and impact puts a toll on it.
