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noname [10]
3 years ago
13

Jenny and Alyssa are members of the cross-country team. On a training run, Jenny starts off and runs at a con-stant 3.8 m/s. Aly

ssa starts 15 s later and runs at a constant 4.0 m/s. At what time after Jenny’s start does Alyssa catch up with Jenny?
Physics
1 answer:
MArishka [77]3 years ago
4 0

Answer:Answer:

300 seconds

Explanation:

We solve this problem using the equation of uniform motion;

d  =v*t

d: Distance traveled

t:  Time

v: Speed

We raise the equations of uniform motion because they run at a constant speed.

dJ=3.8*tJ   Motion equation for Jenny

dA=4*tA   Motion equation for Alyssa

d:distancia

When Jenny and Alissa meet, they will have traveled the same distance,then:

dJ=dA

3.8 tJ  =4*tA

tA =\frac{3.8}{4} * tJ

tA =0.95¨*tJ Equation (1)

Jenny runs 15 seconds longer than Alyssa,then:

tJ = tA+15 Equation (2)

We replace tA =0.95tJ of the Equation (1) in the Equation (2):

tJ = 0.95*tJ +15

tJ-0.95*tJ=15

0.05* tJ=15

tJ=\frac{15}{0.05}

tJ=300 s

Alyssa catch up with Jenny in 300 s after Jenny’s start .

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8 0
2 years ago
Calculate the average drift speed of electrons traveling through a copper wire with a crosssectional area of 80 mm2 when carryin
Vedmedyk [2.9K]

Answer:

The correct answer is 2.8*10^{-5}ms^{-1}

Explanation:

The formula for the electron drift speed is given as follows,

u=I/nAq

where n is the number of of electrons per unit m³, q is the charge on an electron and A is the cross-sectional area of the copper wire and I is the current. We see that we already have A , q and I. The only thing left to calculate is the electron density n that is the number of electrons per unit volume.

Using the information provided in the question we can see that the number of moles of copper atoms in a cm³ of volume of the conductor is 8.93/63.5 molcm^{-3}. Converting this number to m³ using very elementary unit conversion we get 140384molm^{-3}. If we multiply this number by the Avagardo number which is the number of atoms per mol of any gas , we get the number of atoms per m³ which in this case is equal to the number of electron per m³ because one electron per atom of copper contribute to the current. So we get,

n=140384*6.02*10^{23} = 8.45*10^{28}electrons.m^{-3}

if we convert the area from mm³ to m³ we get A=80*10^{-6}m^{2}.So now that we have n, we plug in all the values of A ,I ,q and n into the main equation to obtain,

u=30/(8.45*10^{28}*80*10^{-6}*1.602*10^{-19})\\u=2.8*10^{-5}m.s^{-1}

which is our final answer.

6 0
3 years ago
(URGENT) A ball rolls off a ledge. Its velocity is 7.70m/s in a horizontal direction. It falls on the floor 1.60m below the ledg
elena-s [515]

Answer:

the horizontal distance is 4.355 meters

Explanation:

The computation of the horizontal distance while travelling in the air is shown below:

Data provided in the question is as follows

Velocity = u = 7.70 m/s

H = 1.60 m

R = horizontal direction

Based on the above information

As we know that

R = u × time

where,

Time = \sqrt{\frac{2H}{g} }

So,

= 7.70\times \sqrt{\frac{2\times 1.60}{10} }

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hence, the horizontal distance is 4.355 meters

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3 years ago
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romanna [79]
The answer is why lani

7 0
3 years ago
Weathering of rocks can occur in many ways. In the western United States, strong winds can erode huge rock formations by blowing
stepan [7]

Answer: physical or mechanical weathering

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Mechanical weathering which is also referred to as the physical weathering occurs when a rock is broken down into smaller pieces. In this case, there will be a physical change of the rock but its composition will not change.

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2 years ago
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