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Kruka [31]
3 years ago
5

Marc was told his dinner would be ready at 18:00. He left his house at 12:00 and travelled in his car at an average speed of 45m

ph to his mum's house 300 miles away. Did Marc make it home in time for dinner
Physics
1 answer:
Tema [17]3 years ago
5 0

Answer:

No

Explanation:

<u>No, Marc did not make it on time for dinner.</u>

The time duration between 12:00 and 18:00 is 6 hours.

Total distance that needs to be covered from his house to his mum's house and back = 300 miles x 2 = 600 miles

Time that would be needed to cover 600 miles to his mum's house at an average speed of 45 mph = distance/speed

    = 600/45

            = 13.33 hours

<em>The required time to cover the distance by Marc is approximately 13.33 hours. If he leaves the house by 12:00, he will definitely not get back 6 hours after. Hence, he could not have made it for dinner.</em>

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A tree falls in a forest. How many years must pass before the 14C activity in 1.03 g of the tree's carbon drops to 1.02 decay pe
Illusion [34]

Answer:

t = 5.59x10⁴ y

Explanation:

To calculate the time for the ¹⁴C drops to 1.02 decays/h, we need to use the next equation:

A_{t} = A_{0}\cdot e^{- \lambda t}    (1)

<em>where A_{t}: is the number of decays with time, A₀: is the initial activity, λ: is the decay constant and t: is the time.</em>

To find A₀ we can use the following equation:  

A_{0} = N_{0} \lambda   (2)

<em>where N₀: is the initial number of particles of ¹⁴C in the 1.03g of the trees carbon </em>

From equation (2), the N₀ of the ¹⁴C in the trees carbon can be calculated as follows:        

N_{0} = \frac{m_{T} \cdot N_{A} \cdot abundance}{m_{^{12}C}}

<em>where m_{T}: is the tree's carbon mass, N_{A}: is the Avogadro's number and m_{^{12}C}: is the ¹²C mass.  </em>

N_{0} = \frac{1.03g \cdot 6.022\cdot 10^{23} \cdot 1.3\cdot 10^{-12}}{12} = 6.72 \cdot 10^{10} atoms ^{14}C    

Similarly, from equation (2) λ is:

\lambda = \frac{Ln(2)}{t_{1/2}}

<em>where t 1/2: is the half-life of ¹⁴C= 5700 years </em>

\lambda = \frac{Ln(2)}{5700y} = 1.22 \cdot 10^{-4} y^{-1}

So, the initial activity A₀ is:  

A_{0} = 6.72 \cdot 10^{10} \cdot 1.22 \cdot 10^{-4} = 8.20 \cdot 10^{6} decays/y    

Finally, we can calculate the time from equation (1):

t = - \frac{Ln(A_{t}/A_{0})}{\lambda} = - \frac {Ln(\frac{1.02decays \cdot 24h \cdot 365d}{1h\cdot 1d \cdot 1y \cdot 8.20 \cdot 10^{6} decays/y})}{1.22 \cdot 10^{-4} y^{-1}} = 5.59 \cdot 10^{4} y              

I hope it helps you!

4 0
3 years ago
A block whose weight is 45.8 N rests on a horizontal table. A horizontal force of 36.6 N is applied to the block. The coefficien
Liula [17]

Answer:

Yes it will move and a= 4.19m/s^2

Explanation:

In order for the box to move it needs to overcome the maximum static friction force

Max Static Friction = μFn(normal force)

plug in givens

Max Static friction = 31.9226

Since 36.6>31.9226, the box will move

Mass= Wieght/g which is 45.8/9.8= 4.67kg

Fnet = Fapp-Fk

= 36.6-16.9918

=19.6082

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Solve for a=4.19m/s^2

7 0
3 years ago
To escape from a horrible fire, two people are forced to jump from the third story of a burning building onto solid concrete. Wh
erica [24]
The bouncing person because the bounce helped him survive
8 0
3 years ago
Why does static friction have a maximum value​
Naddik [55]

Answer:

If you push horizontally with a small force, static friction establishes an equal and opposite force that keeps the book at rest. As you push harder, the static friction force increases to match the force. Eventually maximum static friction force is exceeded and the book moves.

Explanation:

3 0
3 years ago
cylindrical container is to be constructed to be open at the top with a volume of 27π cubic meters using the least amount of mat
Llana [10]

Answer:

radius comes out to be 3 m

height of the cylinder comes out to be 3m

Explanation:

given

volume of cylinder = 27π m³

π r² h = 27π

   r² h = 27.............(1)

surface area of cylinder open at the top

S = 2πrh + π r²

S = 2\pi \dfrac{27}{r} + \pi r^2

\frac{\mathrm{d} s}{\mathrm{d} r}=\frac{\mathrm{d}}{\mathrm{d} r} (2\pi \dfrac{27}{r} + \pi r^2)

\frac{\mathrm{d} s}{\mathrm{d} r}=54\pi \dfrac{-1}{r^2}+2\pi r

\frac{\mathrm{d} s}{\mathrm{d} r}=0

for least amount of material requirement.

\dfrac{54\pi }{r^2} = 2\pi r\\r=3m

hence radius comes out to be 3 m

for height put the value in the equation 1

so, height of the cylinder comes out to be 3m

3 0
3 years ago
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