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3 years ago

7

A student performs an experiment and must measure the lengths of four different objects: a textbook, a pencil, a cup, and a piec

e of bread. Which would be the most appropriate unit of measurement for her to use?

2 answers:

Strike441 [17]3 years ago

7 0

Most appropriate unit of measurement should be centimetres, cm.

ehidna [41]3 years ago

6 0

Answer:

Centimeter (cm)

Explanation:

A student performs an experiment and must measure the lengths of four different objects: a textbook, a pencil, a cup, and a piece of bread.

There are so many units of measuring length of an object like centimeter, millimeter, kilometer etc. Some of units are used to measure very large distances (i.e. the distance between sun and earth etc ) are light year, astronomical units etc.

In this case, a textbook, a pencil, a cup, and a piece of bread are small object. The most appropriate unit of measurement for her to use is centimeter or cm.

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A 20.0-kg rock is sliding on a rough, horizontal surface at 8.00 m/s and eventually stops due to friction. The coefficient of ki

Neporo4naja [7]

Answer:

$a = -1.961\,\frac{m}{s^{2}}$ , $s = 16.318\,m$ , $t = 4.079\,s$

Explanation:

The equations of equilibrium for the rock are:

$\Sigma F_{x} = -\mu_{k}\cdot N = m \cdot a$

$\Sigma F_{y} = N - m\cdot g = 0$

After some algebraic handling, the following expression is found:

$-\mu_{k}\cdot m \cdot g = m \cdot a$

$-\mu_{k}\cdot g = a$

Deceleration experimented by the rock is:

$a = - (0.2)\cdot (9.807\,\frac{m}{s^{2}} )$

$a = -1.961\,\frac{m}{s^{2}}$

The distance travelled by the rock before stopping is:

$s = \frac{(0\,\frac{m}{s} )^{2}-(8\,\frac{m}{s} )^{2}}{2\cdot (-1.961\,\frac{m}{s^{2}} )}$

$s = 16.318\,m$

And the time is:

$t = \frac{0\,\frac{m}{s}-8\,\frac{m}{s}}{(-1.961\,\frac{m}{s^{2}} )}$

$t = 4.079\,s$

5 0

3 years ago

Read 2 more answers

A closed, rigid tank fitted with a paddle wheel contains 2 kg of air, initially at 300 K. During an interval of 5 minutes, the p

anzhelika [568]

Answer:

The final temperature of the air is $T_2= 605 K$

Explanation:

We can start by doing an energy balance for the closed system

$\Delta KE+\Delta PE+ \Delta U = Q - W$

where

$\Delta KE$ = the change in kinetic energy.

$\Delta PE$ = the change in potential energy.

$\Delta U$ = the total internal energy change in a system.

Q = the heat transferred to the system.

W = the work done by the system.

We know that there are no changes in kinetic or potential energy, so $\Delta KE = 0$ and $\Delta PE=0$

and our energy balance equation is $\Delta U = Q - W$

We also know that the paddle-wheel transfers energy to the air at a rate of 1 kW and the system receives energy by heat transfer at a rate of 0.5 kW, for 5 minutes.

We use this information to calculate the total internal energy change $\Delta U=W+Q$ using the energy balance equation.

We convert the interval of time to seconds $t = 5 \:min = 300\:s$

$\Delta \dot{U}=\dot{W}+ \dot{Q}\\=\Delta U=(W+ Q)\cdot t$

$\Delta U=(1 \:kW+0.5\:kW)\cdot 300\:s\\\Delta U=450 \:kJ$

We can use the change in specific internal energy $\Delta U = m(u_2-u_1)$ to find the final temperature of the air.

We are given that $T_1=300 \:K$ and the air can be describe by ideal gas model, so we can use the ideal gas tables for air to determine the initial specific internal energy $u_1$

$u_1=214.07\:\frac{kJ}{kg}$

Next, we will calculate the final specific internal energy $u_2$

$\Delta U = m(u_2-u_1)\\\frac{\Delta U}{m} =u_2-u_1$

$\frac{\Delta U}{m} =u_2-u_1\\u_2=u_1+\frac{\Delta U}{m}$

$u_2=214.07 \:\frac{kJ}{kg} +\frac{450 \:kJ}{2 \:kg}\\u_2= 439.07 \:\frac{kJ}{kg}$

With the value $u_2=439.07 \:\frac{kJ}{kg}$ and the ideal gas tables for air we make a regression between the values $u = 434.78 \:\frac{kJ}{kg},T=600 \:K$ and $u = 442.42 \:\frac{kJ}{kg}, T=610 \:K$ and we find that the final temperature $T_2$ is 605 K.

3 0

3 years ago

A 6.9-kg wheel with geometric radius m has radius of gyration computed about its mass center given by m. A massless bar at angle

Vilka [71]

Complete Question

The complete question is shown on the first uploaded image

Answer:

The value is $\alpha =2.538 \ rad/s^2$

Explanation:

From the question we are told that

The mass of the wheel is m = 6.9 kg

The radius is $r = 0.69 \ m$

The radius of gyration is $k_G = 0.4\ m$

The angle is $\theta = 47^o$

The force which the massless bar is subjected to $F = 22.5 \ N$

Generally given that the wheels rolls without slipping on the flat stationary ground surface, it implies that point A is the center of rotation.

Generally the moment of inertia about A is mathematically represented as

$I_a = I_G + M* r^2$

Here $I_G$ is the moment of inertia about G with respect to the radius of gyration which is mathematically represented as

$I_G = M * k_G$

=> $I_a = k_G* M + M* r^2$

=> $I_a =0.4 * 6.9 + 6.9 * 0.69^2$

=> $I_a =6.045 \ kg \cdot m^2$

Generally the torque experienced by the wheel is mathematically represented as

$\tau = F * cos (47)$

=> $\tau = 22.5 * cos (47)$

=> $\tau = 15.34 \ kg \cdot m^2 \cdot s^{-2}$

Generally this torque is also mathematically represented as

$\tau = I_a * \alpha$

=> $15.34 = 6.045 * \alpha$

=> $\alpha =2.538 \ rad/s^2$

4 0

3 years ago

A vector has a component of 10 m in the x-direction, a component of 10 m in the y-direction, and a component of 5 m in the z dir

Kobotan [32]

The magnitude of this vector is 15

A vector is a quantity or phenomenon that has two independent properties: magnitude and direction. The term also denotes the mathematical or geometrical representation of such a quantity. Examples of vectors in nature are velocity, momentum, force, electromagnetic fields, and weight.

The magnitude of a vector formula is used to calculate the length for a given vector (say v) and is denoted as |v|. So basically, this quantity is the length between the initial point and endpoint of the vector.

Let vector be = a

component of vector in x direction = 10 i

component of vector in y direction = 10 j

component of vector in z direction = 5 z

vector a = 10 i + 10 j + 5 z

magnitude of vector a = |a| = $\sqrt{10^{2} +10^{2} + 5^{2} }$

= 15

To learn more about vector here

brainly.com/question/24256726

#SPJ4

8 0

2 years ago

The newest generation of smart phone uses three different batteries connected in a series simultaneously to extend battery life

azamat

Answer:

7.2 V

Explanation:

The three batteries are connected in series to the terminals of the phone: it means that they are connected along the same branch, so the current flowing through them is the same.

This also means that the potential difference across the phone will be equal to the sum of the voltages provided by each battery.

Here, the voltage provided by each battery is

V = 2.4 V

So, the overall voltage will be

V = 2.4 V + 2.4 V + 2.4 V = 7.2 V

8 0

3 years ago