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2 years ago

A car is moving at a rate of 72km/hr . How far does the car move when it stops after 4 seconds?

Physics

2 answers:

oee [108]2 years ago

8 0

Answer:

The car will stop after 4 seconds after moving the distance of 0.08km.

Explanation:

The reading above it clearly states that a car is moving at a speed of 72Km/hr. And it asking for the distance the car move when it stops after 4 seconds.

Looking at speed formula , speed=distance÷time.

But in this problem we I finding distance, so in speed formula make distance the subject.

<h3>Therefore distance = speed × time</h3>

Before going ahead you should have this in mind the unit for distance is Km and m . Our speed is in Km/hr but our time is in second. In this case change 4 seconds to hour which is 0.00111 hr .you change second to hour because hr will cancel hr when solving for distance giving distance unit Km

Distance = speed × time

Distance= 72km/hr × 0.00111 hr

hour cancel hour

Distance= 72km × 0.00111

Distance = 0.08km

Therefore the car will stop after 4 seconds after moving the distance of 0.08km.

Please mark brainliest.

kari74 [83]2 years ago

5 0

conversion :

72 km/h = 72 × (1000/3600) = 20 m/s

so, in 4 seconds it travel

4 × 20 = 80 meters = 0.08 km

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A student measures the diameter of a small cylindrical object and gets the following readings: 4.32, 4.35, 4.31, 4.36, 4.37, 4.3

Zinaida [17]

Answer:

a. $\bar{d}=4.34 cm$

b. $\sigma=0.023 cm$

c. $\rho=(0.0089\pm 0.00058) kg/cm^{3}$

Explanation:

a) The average of this values is the sum each number divided by the total number of values.

$\bar{d}=\frac{\Sigma_{i=1}^(N)x_{i}}{N}$

$x_{i}$ is values of each diameter
N is the total number of values. N=6

$\bar{d}=\frac{4.32+4.35+4.31+4.36+4.37+4.34}{6}$

$\bar{d}=4.34 cm$

b) The standard deviation equations is:

$\sigma=\sqrt{\frac{1}{N}\Sigma^{N}_{i=1}(x_{i}-\bar{d})^{2}}$

If we put all this values in that equation we will get:

$\sigma=0.023 cm$

Then the mean diameter will be:

$\bar{d}=(4.34\pm 0.023)cm$

c) We know that the density is the mass divided by the volume (ρ = m/V)

and we know that the volume of a cylinder is: $V=\pi R^{2}h$

Then:

$\rho=\frac{m}{\pi R^{2}h}$

Using the values that we have, we can calculate the value of density:

$\rho=\frac{1.66}{3.14*(4.34/2)^{2}*12.6}=0.0089 kg/cm^{3}$

We need to use propagation of error to find the error of the density.

$\delta\rho=\sqrt{\left(\frac{\partial\rho}{\partial m}\right)^{2}\delta m^{2}+\left(\frac{\partial\rho}{\partial d}\right)^{2}\delta d^{2}+\left(\frac{\partial\rho}{\partial h}\right)^{2}\delta h^{2}}$

δm is the error of the mass value.
δd is the error of the diameter value.
δh is the error of the length value.

Let's find each partial derivative:

1. $\frac{\partial\rho}{\partial m}=\frac{4m}{\pi d^{2}h}=\frac{4*1.66}{\pi 4.34^{2}*12.6}=0.0089$

2. $\frac{\partial\rho}{\partial d}=-\frac{8m}{\pi d^{3}h}=-\frac{8*1.66}{\pi 4.34^{3}*12.6}=-0.004$

3. $\frac{\partial\rho}{\partial h}=-\frac{4m}{\pi d^{2}h^{2}}=-\frac{4*1.66}{\pi 4.34^{2}*12.6^{2}}=-0.00071$

Therefore:

$\delta\rho=\sqrt{\left(0.0089)^{2}*0.05^{2}+\left(-0.004)^{2}*0.023^{2}+\left(-0.00071)^{2}*0.5^{2}}$

$\delta\rho=0.00058$

So the density is:

$\rho=(0.0089\pm 0.00058) kg/cm^{3}$

I hope it helps you!

3 0

3 years ago

Three masses (3 kg, 5 kg, and 7 kg) are located in the xy-plane at the origin, (2.3 m, 0), and (0, 1.5 m), respectively.

Artist 52 [7]

Answer:

a) C.M $=(\bar x, \bar y)=(0.767,0.7)m$

b) $(x_4,y_4)=(-1.917,-1.75)m$

Explanation:

The center of mass "represent the unique point in an object or system which can be used to describe the system's response to external forces and torques"

The center of mass on a two dimensional plane is defined with the following formulas:

$\bar x =\frac{\sum_{i=1}^N m_i x_i}{M}$

$\bar y =\frac{\sum_{i=1}^N m_i y_i}{M}$

Where M represent the sum of all the masses on the system.

And the center of mass C.M $=(\bar x, \bar y)$

Part a

$m_1= 3 kg, m_2=5kg,m_3=7kg$ represent the masses.

$(x_1,y_1)=(0,0),(x_2,y_2)=(2.3,0),(x_3,y_3)=(0,1.5)$ represent the coordinates for the masses with the units on meters.

So we have everything in order to find the center of mass, if we begin with the x coordinate we have:

$\bar x =\frac{(3kg*0m)+(5kg*2.3m)+(7kg*0m)}{3kg+5kg+7kg}=0.767m$

$\bar y =\frac{(3kg*0m)+(5kg*0m)+(7kg*1.5m)}{3kg+5kg+7kg}=0.7m$

C.M $=(\bar x, \bar y)=(0.767,0.7)m$

Part b

For this case we have an additional mass $m_4=6kg$ and we know that the resulting new center of mass it at the origin C.M $=(\bar x, \bar y)=(0,0)m$ and we want to find the location for this new particle. Let the coordinates for this new particle given by (a,b)

$\bar x =\frac{(3kg*0m)+(5kg*2.3m)+(7kg*0m)+(6kg*a)}{3kg+5kg+7kg+6kg}=0m$

If we solve for a we got:

$(3kg*0m)+(5kg*2.3m)+(7kg*0m)+(6kg*a)=0$

$a=-\frac{(5kg*2.3m)}{6kg}=-1.917m$

$\bar y =\frac{(3kg*0m)+(5kg*0m)+(7kg*1.5m)+(6kg*b)}{3kg+5kg+7kg+6kg}=0m$

$(3kg*0m)+(5kg*0m)+(7kg*1.5m)+(6kg*b)=0$

And solving for b we got:

$b=-\frac{(7kg*1.5m)}{6kg}=-1.75m$

So the coordinates for this new particle are:

$(x_4,y_4)=(-1.917,-1.75)m$

5 0

3 years ago

Solve the problem using dimensional analysis. Every number must have a unit. Work must be shown. Conversion factors are in the t

anygoal [31]

The number of grams of gold you can purchase for $15 if Gold cost $8.00 per ounce is 53.26g

Dimensional analysis is a means of representing values using units.

From the question, we are told that Gold cost $8.00 per ounce, this means that:

$8.00 = 1 ounce

In order to calculate the amount in grams you can purchase for $15, we need to know the price in ounces first.

$15.00 = x

Divide both expressions

$\dfrac{8}{15} = \dfrac{1}{x}\\x = \dfrac{15}{8}\\x= 1.875 ounces$

Next is to convert the ounces to pounds.

1 pound = 16 ounces

y = 1.875 ounces

y = 1.875/16

y = 0.1171875 pounds

Conver 0.1171875 pounds to kg

Since 1kg = 2.2 pounds

z = 0.1171875 pounds

2.2z = 0.1171875

z = 0.1171875/2.2

z = 0.053267kg

Finally, convert 0.053267kg to grams using the conversion rate

1kg = 1000g

0.053267kg = y

y = 0.05326 * 1000

y = 53.26g

This shows that the amount of grams you can purchase for $15 is 53.26g

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5 0

3 years ago

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jeka94

Order to ensure a message is understood requires all four option is needed.

The option will be D.All of the above.

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The sender is the person who is trying to communicate a message.
The challenge is that since the receiver’s education and experience may be very different from the sender's, words often have different meanings.
While we may carefully choose the words to speak, words alone represent a small percentage.
communication is only verbal the most important element of communication
When encountering a noise, take steps to reduce the distraction.

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2 years ago

Read 2 more answers

Can someone tell me the answer and the reason

spin [16.1K]

Answer:

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The surface is smooth, therefore coefficient of friction is tending to zero.

Forces for each blocks varied from 6N to 8N to 7N to 5N

The blocks were made of different materials and different materials are going to have varying weight for the same size of block.

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4 years ago