Answer:
Option B. 32 g
Explanation:
From the question given above, the following data were obtained:
Original amount (N₀) = 128 g
Half-life (t½) = 2.25 billion years
Number of half-lives (n) = 2
Amount remaining (N) =?
The amount of 128 gram of Radium-226 that will remain after 2 half-lives has elapsed can be obtained as followb
N = 1/2ⁿ × N₀
N = 1/2² × 128
N = 1/4 × 128
N = 0.25 × 128
N = 32 g
Therefore, 32g of the sample will remain.
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
Answer:
c. about 1/10 as great.
Explanation:
While jumping form a certain height when we bend our knees upon reaching the ground such that the time taken to come to complete rest is increased by 10 times then the impact force gets reduced to one-tenth of the initial value when we would not do so.
This is in accordance with the Newton's second law of motion which states that the rate of change in velocity is directly proportional to the force applied on the body.
Mathematically:
![F\propto\frac{d}{dt} (p)](https://tex.z-dn.net/?f=F%5Cpropto%5Cfrac%7Bd%7D%7Bdt%7D%20%28p%29)
![\Rightarrow F=\frac{d}{dt} (m.v)](https://tex.z-dn.net/?f=%5CRightarrow%20F%3D%5Cfrac%7Bd%7D%7Bdt%7D%20%28m.v%29)
since mass is constant
![F=m\frac{d}{dt}v](https://tex.z-dn.net/?f=F%3Dm%5Cfrac%7Bd%7D%7Bdt%7Dv)
when ![dt=10t](https://tex.z-dn.net/?f=dt%3D10t)
then,
![F'=m.\frac{v}{10\times t}](https://tex.z-dn.net/?f=F%27%3Dm.%5Cfrac%7Bv%7D%7B10%5Ctimes%20t%7D)
![F'=\frac{1}{10} \times \frac{m.v}{t}](https://tex.z-dn.net/?f=F%27%3D%5Cfrac%7B1%7D%7B10%7D%20%5Ctimes%20%5Cfrac%7Bm.v%7D%7Bt%7D)
the body will experience the tenth part of the maximum force.
where:
represents the rate of change in dependent quantity with respect to time
momentum
mass of the person jumping
velocity of the body while hitting the ground.
Answer:
8 KJ/ s
Explanation:
Heat pumps Transfer thermal energy through absorbing of heat that comes from cold region and then release to warmer area by utilizing external power.
The coefficient of performance known as COP provide the ratio of both heating and cooling that are supplied to required work.
✓QH=The rate at which heat is produced = ?
✓COP= Coefficient of performance of a residential heat pump = 1.6
✓ W(in)= power consumption= 5KW
QH=The rate at which heat is produced=[Coefficient of performance of a residential heat pump] × [power consumption]
= 1.6 × 5KW
=8 KJ/ s