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3 years ago

If we start with 48 g of a radioactive substance with a 2 hour 12 life, how much is left after two half-lives?

Physics

1 answer:

ivolga24 [154]3 years ago

4 0

Explanation:

Half-life is the time taken for a radioactive material to decay to half its original composition:

Original mass = 48g

Half- life = 2hr

After four half lives;

Initially: 48g

First halving 24

Second halving 12

Third halving 6

Fourth halving 3

After second half life, we would have 12g

At fourth halving, we would have 3g

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A car going initially with a velocity 13.5 m/s accelerates at a rate of 1.9 m/s for 6.2 s. It then accelerates at a rate of-1.2

yanalaym [24]

Answer:

a) Maximum speed = 25.28 m/s

b) Total time = 27.27 s

c) Total distance traveled = 402.43 m

Explanation:

a) Maximum speed is obtained after the end of acceleration

v = u + at

v = 13.5 + 1.9 x 6.2 = 25.28 m/s

Maximum speed = 25.28 m/s

b) We have maximum speed = 25.28 m/s, then it decelerates 1.2 m/s² until it stops.

v = u + at

0 = 25.28 - 1.2 t

t = 21.07 s

Total time = 6.2 + 21.07 = 27.27 s

c) Distance traveled for the first 6.2 s

s = ut + 0.5 at²

s = 13.5 x 6.2 + 0.5 x 1.9 x 6.2² = 120.22 m

Distance traveled for the second 21.07 s

s = ut + 0.5 at²

s = 25.28 x 21.07 - 0.5 x 1.2 x 21.07² = 282.21 m

Total distance traveled = 120.22 + 282.21 = 402.43 m

5 0

3 years ago

Read 2 more answers

Please help! the mass of an object is measured on a pan balance with a precision of 0.005 g and the recorded value of 128.01 g.

inysia [295]

Yes, these two objects have different masses.

<h3>How can we calculate that this statement is right ?</h3>

To calculate the precision of mass we are using the formula,

Precision(P) = $\frac{m_1}{m_1+\triangle m}$

Or, $\triangle$ m= $\frac{m_1}{P}$ -m₁

For the first case we are given,

m₁= The recorded value of mass

= 128.01 g

P= Precision of the mass

=0.005g

So, according to the formula, $\triangle$ m will be,

$\triangle$ m= $\frac{128.01}{0.005}$ -128.01

Or, $\triangle$ m=25,473.99 g

Or, $\triangle$ m=25.47 Kg

For the first case $\triangle$ m is 25.47 Kg..

For the second case we are given,

m₁= The recorded value of mass

= 0.13 Kg

P= Precision of the mass

=0.005 Kg

So, according to the formula, $\triangle$ m will be,

$\triangle$ m= $\frac{0.13}{0.005}$ -0.13

Or, $\triangle$ m= 25.87 kg

For the second case $\triangle$ m is 25.87 Kg.

For the two cases $\triangle$ m has different values, 25.47 Kg≠25.87 Kg.

Therefore we can conclude that, these two objects have different masses.

Learn more about Mass:

brainly.com/question/3187640

#SPJ4

7 0

2 years ago

The space probe Deep Space 1 was launched on October 24th, 1998 and it used a type of engine called an ion propulsion drive. An

Xelga [282]

Answer:

Explanation:

mass of probe m = 474 Kg

initial speed u = 275 m /s

force acting on it F = 5.6 x 10⁻² N

displacement s = 2.42 x 10⁹ m

A )

initial kinetic energy = 1/2 m u² , m is mass of probe.

= .5 x 474 x 275²

= 17923125 J

B )

work done by engine

= force x displacement

= 5.6 x 10⁻² x 2.42 x 10⁹

= 13.55 x 10⁷ J

C ) Final kinetic energy

= Initial K E + work done by force on it

= 17923125 +13.55 x 10⁷

= 1.79 x 10⁷ + 13.55 x 10⁷

= 15.34 x 10⁷ J

D ) If v be its velocity

1/2 m v² = 15.34 x 10⁷

1/2 x 474 x v² = 15.34 x 10⁷

v² = 64.72 x 10⁴

v = 8.04 x 10² m /s

= 804 m /s

5 0

3 years ago

Which of the following is not a reason fluorescent lamps are advantageous over incandescent lamps?

cricket20 [7]

Answer;

B. Fluorescent lamps operate at a higher temperature than incandescent lamps.

Explanation;

-A fluorescent lamp, is a type of electric light (lamp) that uses ultraviolet emitted by mercury vapor to excite a phosphor, which emits visible light.

-A fluorescent lamp produces less heat, thus, it is much more efficient. A fluorescent bulb can produce between 50 and 100 lumens per watt. This makes fluorescent bulbs four to six times more efficient than incandescent bulbs.

-Fluorescent lamps operate best around room temperature. At much lower or higher temperatures, efficacy decreases.

4 0

3 years ago

Read 2 more answers

Albert presses a book against a wall with his hand. As Albert gets tired, he exerts less force, but the book remains in the same

marissa [1.9K]

Answer:

maximum static frictional force of the wall on the book (Increasing)

normal force of the wall on the book (Decreasing)

weight of the book (Not changing)

Explanation:

Now according to Newton's third law of motion

"Every action has equal but opposite reaction"

By the data given in question, Albert was pressing the book against the wall.Now, Albert started to reduce his force up against the wall.

First we have to consider all the forces applied on book in this scenario.

1. Weight of book acting downwards (y-axis)

2. Friction between book and wall acting upward (y-axis)

3. Albert's force on book against wall (x-axis)

4. Normal reaction of wall against Albert's force (x-axis)

Now, when Albert reduced his force, new scenario will be

1. Weight will be remain constant as it is W = mg

Neither mass nor acceleration due to gravity changed, so weight acting upon the book will remain same.

2. When Albert reduced force, normal reaction of wall reduced against it according to Newton's third law of motion

3. Now notice that friction is a force which acts in accordance with the applied force. For example if a box is placed at floor, no friction is applied, but when you drag the box, friction starts to act and increases until its limit comes. So, when Albert reduced his force, weight will try to pull the book and maximum static friction will increase to hinder the movement of book downwards.

Notice that maximum static friction will hinder the book from movement, since Albert reduced his force, but wight didn't pull the book, which means that maximum static friction increased to hinder downward motion.

7 0

3 years ago