Answer: C
14.75g
Explanation:
Given that the half life time = 60.5s
Let No = initial mass = 59g
N = decayed mass
At time t = 0, No = 59g
At time t = 60.5s,
N = No/2 = 59/2
= 29.5g
At time t = 121
N = 29.5/2 = 14.75g
Therefore N = 14.75g
Answer:
817.5 Pa
Explanation:
From Bernoulli's equation, considering thst there is no height difference then
P1+½d(v1)²=P2+½d(v2)²
P1-P2=½d(v2²-v1²)
∆P=½d(v2²-v1²)
Where P represent pressure, d is density and v is velocity. Subscripts 1 and 2 represent inside and outside. ∆P is tge change in pressure
Given the speed at roof top as 128 km/h, we convert it to m/s as follows
128*1000/3600=35.555555555555=35.56 m/s
Velocity at the bottom of roof is 0 m/s
Density is given as 1.293 kg/m³
∆P=½*1.293*(35.56²-0)=817.5 Pa
Answer:
B. QC > 0; QH < 0
Explanation:
Given that there are two reservoir of energy.
Sign convention for heat and work :
1.If the heat is adding to the system then it is taken as positive and if heat is going out from the system then it is taken as negative.
2. If the work is done on the system then it is taken as negative and if the work is done by the system then it is taken as positive.
From hot reservoir heat is going out that is why it is taken as negative
From cold reservoir heat is coming inside the reservoir that is why it is taken as positive
That is why the answer will be
,
Answer:
True statements:
Power is the rate at which work is done.
Power is the rate at which energy is transformed.
The SI unit of power is watt.
A person is limited in the total work he or she can do by the rate at which energy can be transformed.
Explanation:
The above statements are true.
1. Power is defined as the rate at which work is done.
2. Power is the rate at which energy is transformed. Whenever energy changes its form, or moves from one place to another, the rate at which it makes those changes is described as power.
3. The SI Unit of power is watts. If 1 joule of energy is converted by an object in 1 second then its power is called one watt.
So, the statement<em> 'the SI unit of power is the horsepower' is</em> false.
4. A person is limited in the total work he or she can do by the rate at which energy can be transformed i.e, his power. He is not only limited by the total energy required.
So, the statement <em>'A person is limited in the total work he or she can do only by the total energy required'</em> is not completely true.
The formular for determinatio of mass number is this:
Mass number = number of proton + number of neutron
From the question, we are told that:
Mass number = 39
Proton number = 19
Number of proton = ?
Number of neutron = mass number - number of proton
Number of neutron= 39 - 19 = 20
Therefore, number of neurtron = 20.
