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madam [21]
3 years ago
8

The C-14 decay is used to estimate the age of an old dead tree. The activity of C-14 in the dead tree is determined to have fall

en to 21% of its original value. C-14 has a half-life of 5700 years. Calculate, in years, the age of the dead tree.
I used the relevant formula but somehow my answer does not match with the markscheme. Can you help me?
Physics
1 answer:
meriva3 years ago
7 0
From the calculations i did, its 1197. Is that the one you got?
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A student wants to use a ramp to move boxes into a truck bed that is 3 m high. He has a choice of 2 different ramps. The length
Morgarella [4.7K]

Answer:

The correct option is;

B. 8 m, because he has to apply less force over a greater distance

Explanation:

In the given question, in order for the student to lift the boxes onto the tuck with less amount of force, he applies the principle of Mechanical Advantage

The mechanical advantage is given by the measure by which a force is amplified through the use of a tool

Given that the work done = The force × The distance, we have

F₁ × d₁ = F₂ × d₂, which gives;

d₁/d₂ = F₂/F₁

Where;

F₁ = The input force

F₂ = The output force

d₁ = The input distance

d₂ = The output distance

The Mechanical advantage, MA = d₁/d₂ = F₂/F₁

Therefore, when the input distance is increased the input force will be reduced for a given output force

6 0
3 years ago
A 100 mH inductor whose windings have a resistance of 6.0 Ω is connected across a 12 Vbattery having an internal resistance of 3
Alexus [3.1K]

Answer:

The store energy in the inductor is 0.088 J

Explanation:

Given that,

Inductor = 100 mH

Resistance = 6.0 Ω

Voltage = 12 V

Internal resistance = 3.0 Ω

We need to calculate the current

Using ohm's law

V = IR

I=\dfrac{V}{R+r}

Put the value into the formula

I=\dfrac{12}{6.0+3.0}

I=1.33\ A

We need to calculate the store energy in the inductor

U=\dfrac{1}{2}LI^2

U=\dfrac{1}{2}\times100\times10^{-3}\times(1.33)^2

U=0.088\ J

Hence, The store energy in the inductor is 0.088 J

7 0
3 years ago
What is the minimum mass needed for a star to be on the main sequence? What happens to stars that do not meet the minimum mass?
Mariana [72]
Main sequence stars are characterised by the source of their energy.They are all undergoing fusion of hydrogen into helium within their cores. The mass of the star is the main element for such process or phenomenon to take place for it is a determinant of both the rate at which they perform the said activity and the amount of fuel available. 

To answer the question, the lower mass limit for a main sequence star is about 0.08. If the mass of a main sequence star is lower than the above-mentioned value, there would be a deficit or insufficiency of gravitational force to generate a standard temperature for hydrogen core fusion to take place and the underdeveloped star would form into a brown dwarf instead.
6 0
3 years ago
A meter stick is held vertically with one end on the floor and is then allowed to fall. Find the speed of the other end when it
Tems11 [23]

Answer:

5.4 ms⁻¹

Explanation:

Here we have to use conservation of energy. Initially when the stick is held vertical, its center of mass is at some height above the ground, hence the stick has some gravitational potential energy. As the stick is allowed to fall, its rotates about one. gravitational potential energy of the stick gets converted into rotational kinetic energy.

L = length of the meter stick = 1 m

m = mass of the meter stick

w = angular speed of the meter stick as it hits the floor

v = speed of the other end of the stick

we know that, linear speed and angular speed are related as

v = r w\\w = \frac{v}{r}

h = height of center of mass of meter stick above the floor = \frac{L}{2} = \frac{1}{2} = 0.5 m

I = Moment of inertia of the stick about one end

For a stick, momentof inertia about one end has the formula as

I = \frac{mL^{2} }{3}

Using conservation of energy

Rotational kinetic energy of the stick = gravitational potential energy

(0.5) I w^{2} = mgh\\(0.5)(\frac{mL^{2} }{3}) (\frac{v}{L} )^{2} = mgh\\(0.5)(\frac{v^{2} }{3}) = gh\\(0.5)(\frac{v^{2} }{3}) = (9.8)(0.5)\\v = 5.4 ms^{-1}

7 0
3 years ago
Why do some objects fall faster than others?
monitta

Answer:

Weight and Mass !!!!!!

Explanation:

Galileo discovered that objects that are more dense, or have more mass, fall at a faster rate than less dense objects, due to this air resistance. A feather and brick dropped together. Air resistance causes the feather to fall more slowly.

3 0
3 years ago
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