All categories

3 years ago

What is the half-life of a radioactive isotope that decreases to one fourth its original amount in 18 months

Physics

1 answer:

just olya [345]3 years ago

7 0

9 months, because half of 18 is 9

You might be interested in

A 3.0-kg block is on a horizontal surface. The block is at rest when, at t = 0, a force (magnitude P = 12 N) acting parallel to

GarryVolchara [31]

Explanation:

It is given that,

Mass of the block, m = 3 kg

Initially, the block is at rest, u = 0

Force acting on the block, P = 12 N

The coefficient of kinetic friction between the block and the surface is, $\mu_k=0.2$

We need to find the rate is the force P doing work on the block at t = 2.0 s. The rate at which work is done is called the power. Let is equal to P'

Frictional force acting on the block, $f=\mu_k mg$

$f=0.2\times 3\ kg\times 9.8\ m/s^2=5.88\ N$

So, the net force acting on the block, F = P - f

$F=12-5.88=6.12\ N$

Let a is the acceleration of the block, $a=\dfrac{F}{m}$

$a=\dfrac{6.12}{3}=2.04\ m/s^2$

Let v is the velocity of the block after 2 seconds. So,

$v=u+at$

$v=0+2.04\times 2$

v = 4.08 m/s

Power, $P'=\dfrac{W}{t}=\dfrac{F.d}{t}=F.v$

$P'=12\ N\times 4.08\ m/s=48.96\ Watts$

So, the force P is doing work on the block at the rate of 48.96 watts.

3 0

3 years ago

Which feature of a heating curve indicates a change of state

ziro4ka [17]

Answer:

The diagonal or the inclined lines shows the changes in terms of temperature, and the horizontal lines shows the changing of phases.

Explanation:

hope it is useful

3 0

3 years ago

Urgent ex 5 si 4 va rog mult

maks197457 [2]

Answer:

are you college ?????????

8 0

3 years ago

Identify the equation used to calculate the perpendicular force (F⊥) acting on a block on an inclined plane.

pychu [463]

Using geometrical arguments, we can see that the angle of the inclined plane $\theta$ is equal to the angle between Fg and the perpendicular force.

But the perpendicular force is the projection of Fg along the perpendicular axis, and Fg=mg, so the correct answer is
<span>C) F=mg cosΘ </span>

6 0

3 years ago

Read 2 more answers

True or false

ElenaW [278]

If im not mistaken it is true

4 0

3 years ago