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3 years ago

A car accelerates from rest at 3.6 m/s 2 . How much time does it need to attain a speed of 5 m/s?

Physics

1 answer:

Olenka [21]3 years ago

6 0

car starts from rest

$v_i = 0$

final speed attained by the car is

$v_f = 5 m/s$

acceleration of the car will be

$a = 3.6 m/s^2$

now the time to reach this final speed will be

$t = \frac{v_f - v_i}{a}$

$t = \frac{5 - 0}{3.6}$

$t = 1.39 s$

so it required 1.39 s to reach this final speed

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Why is the crank on a meat grinder larger than the crank on a pencil

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It takes more work to use a meat grinder

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3 years ago

Read 2 more answers

Which three quantities can be used to calculate acceleration?

PtichkaEL [24]

D is the correct answer, assuming that this is the special case of classical kinematics at constant acceleration. You can use the equation V = Vo + at, where Vo is the initial velocity, V is the final velocity, and t is the time elapsed. In D, all three of these values are given, so you simply solve for a, the acceleration.
A and C are clearly incorrect, as mass and force (in terms of projectile motion) have no effect on an object's motion. B is incorrect because it is not useful to know the position or distance traveled, unless it will help you find displacement. Even then, you would not have enough information to use a kinematics equation to find a.

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3 years ago

Given that an electric field of 3×106V/m3×106V/m is required to produce an electrical spark within a volume of air, estimate the

Andre45 [30]

Answer:

Length, l = 33.4 m

Explanation:

Given that,

Electrical field, $E=3\times 10^6\ V/m$

Let the electrical potential is, $V=10^8\ V$

We need to find the length of a thundercloud lightning bolt. The relation between electric field and the electric potential is given by :

$V=E\times d\\\\d=\dfrac{V}{E}\\\\d=\dfrac{10^8}{3\times 10^6}\\\\d=33.4\ m$

So, the length of a thundercloud lightning bolt is 33.4 meters. Hence, this is the required solution.

5 0

3 years ago

Some hypothetical alloy is composed of 12.5 wt% of metal A and 87.5 wt% of metal B. If the densities of metals A and B are 4.27

densk [106]

Answer:

The number of atoms in the unit cell is 2, the crystal structure for the alloy is body centered cubic.

Explanation:

Given that,

Weight of metal A = 12.5%

Weight of metal B = 87.5%

Length of unit cell = 0.395 nm

Density of A = 4.27 g/cm³

Density of B= 6.35 g/cm³

Weight of A = 61.4 g/mol

Weight of B = 125.7 g/mol

We need to calculate the density of the alloy

Using formula of density

$\rho=n\times\dfrac{m}{V_{c}\times N_{A}}$

$n=\dfrac{\rho\timesV_{c}\times N}{m}$ ....(I)

Where, n = number of atoms per unit cells

m = Mass of the alloy

V=Volume of the unit cell

N = Avogadro number

We calculate the density of alloy

$\rho=\dfrac{1}{\dfrac{12.5}{4.27}+\dfrac{87.5}{6.35}}\times100$

$\rho=5.98$

We calculate the mass of the alloy

$m=\dfrac{1}{\dfrac{12.5}{61.4}+\dfrac{87.5}{125.7}}\times100$

$m=111.15$

Put the value into the equation (I)

$n=\dfrac{5.9855\times(0.395\times10^{-9}\times10^{2})^3\times6.023\times10^{23}}{111.15}$

$n=1.99\approx 2\ atoms/cell$

Hence, The number of atoms in the unit cell is 2, the crystal structure for the alloy is body centered cubic.

5 0

3 years ago

Choose the correct answer

irina1246 [14]

Answer:

The average velocity has magnitude = 10 km/h , direction: east

Explanation:

In order to find the average velocity of the car we need to know the final and initial positions, and the time that took to get from one to the other.

Notice that since its movement was 60 km straight east and then from there 40 km straight west, the car is positioned at 20 km to the east of its initial departure point. therefore the vector change in position is a vector 20 km in magnitude, and direction towards the east.

Since it took the car a total of 1.33 hours plus 0.67 hours to reach its final position, the total time elapsed is: 1.33 + 0.67 hours = 2 hours.

Then,the velocity vector has magnitude; 20 km / 2 hours = 10 km/hour

As we mentioned above. the direction of the velocity vector is east.

6 0

2 years ago