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storchak [24]
3 years ago
7

Choose the correct statement concerning units of power or energy. a. A kilojoule (kJ) is a unit of power. b. A gigawatt (GW) is

a unit of energy. c. A watt (W) is a unit of energy. d. A kilowatt x hour per year (kWh/yr) is a unit of energy. e. A kilowatt (kW) is a unit of power.
Physics
1 answer:
sergiy2304 [10]3 years ago
3 0

Answer:

A kilowatt (kW) is a unit of power.

Explanation:

The power of an object is given by :

P=\dfrac{E}{t}

Here,

E is the energy required

t is time

The SI unit of power is Watts and the SI unit of energy is Joule. the commercial unit of energy is kilowatt per hour.    

Option (1) :  A kilojoule (kJ) is a unit of power is incorrect.

Option (2) : A gigawatt (GW) is a unit of energy is incorrect.

Option (3) : A watt (W) is a unit of energy is incorrect.

Option (4) : A kilowatt x hour per year (kWh/yr) is a unit of energy is incorrect.

Option (4) : A kilowatt (kW) is a unit of power is correct.

Hence, the correct option is (d).

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An airplane undergoes the following displacements, all at the same altitude: First, it flies 59.0 km in a direction 30.0° east o
ddd [48]

Answer:

B) 71.5 [km]

Explanation:

To solve this problem we will decompose each of the directions in the x & y axes.

To solve this problem we will decompose each of the directions in the x & y axes. also for a greater understanding of the angles, you should look at the attached image, which contains the orientations for each angle (clockwise or counterclockwise).

<u>59.0 km in a direction 30.0° east of north</u>

<u />

d_{1x}= 59*sin(30) = 29.5[km]\\d_{1y}= 59*cos(30) = 51.09[km]

<u>58.0 km due south</u>

<u />

d_{2y} = - 58 [km]\\

<u>It flies 100 km 30.0° north of west</u>

<u />

<u />d_{3x}= - 100*cos(30) = -86.6[km]\\d_{3y} = 100*sin(30)= 50 [km]<u />

<u />

Now we sum algebraically the components

d_{x}=29.5-86.6 = -57.1[km]\\d_{y}=51.09 -58+50=43.09[km]\\\\

Using the Pythagorean theorem we can find the magnitude of the displacement.

d = \sqrt{(57.1)^{2} +(43.09)^{2} } \\d= 71.53[km]

7 0
3 years ago
An object is formed by attaching a uniform, thin rod with a mass of mr = 6.9 kg and length L = 4.88 m to a uniform sphere with m
Bumek [7]

Answer:

a)  total moment of inertia is 1359.05 kg m^2

b) angular acceleratio is 0.854rad/sec^2

Explanation:

Given data:

m1=6.9 kg

L=4.88 m

m2=34.5 kg

R=1.22 m

we klnow that moment of inertia for rod is given as

J1=(1/12) ×m×L^2

J1 = (1/12) \times 6.9 \times 4.88^2 = 13.693 kg m^2

moment of inertia for sphere is given as

J1=(2/5) ×m×r^2

J1 = (2/5) \times 34.5 \times 1.22^2 = 20.539 kg m^2

As object rotates around free end of rod then for sphere the axis around what it rotates is at a distance of d2=L+R

For rod distance is  d1=0.5*L

By Steiner theorem

for the rod we get J_1'=J_1 + m_1\times d_1^2

J_1' = 13.693 + 2.44^2\times 6.9 = 54.77 kg m^2

for the sphere we get J_2' = J_2 + m_2\times d_2^2

J2' = 20.539 + 34.5\times 6.1^2 = 1304.28 kg^m2

And the total moment of inertia for the first case is

J_{t1} = J_1'+J_2' = 54.77 + 1304.28 = 1359.05kg.m^2

b) F=476 N

The torque for system is given as

M = F\times d\times sin(a)

where a is angle between Force and distance d

and where d represent distance from rotating axis.

In this case a = 90 degree  

M = F\times L/2

M=476*2.44 = 1161.44 Nm

The acceleration is calculated as

a_1 = \frac{M}{J_{t1}}

      = \frac{1161.44}{1359.05}

      = 0.854 rad/sec^2

4 0
3 years ago
Pleaseeeee help!! It’s due very soon
iris [78.8K]

Answer:

accelerated motion

Explanation:

a change in velocity (10 m/s to 50 m/s) over time (5 s) is called acceleration.

40/5 = 8 m/s²

6 0
3 years ago
What changes must be done to the wire to increase its conductance.​
777dan777 [17]

Answer:

- Decreasing the resistance

- Using a shorter length

- Using a smaller area wire

Explanation:

Formula for conductance in wires is;

G = 1/R

Where;

G is conductance

R is resistance

This means that increasing the resistance leads to a larger denominator and thus a smaller conductance but to decrease the denominator means larger conductance.

Thus, to increase the conductance, we have to decrease the resistance.

Resistance here has a formula of;

R = ρL/A

Where;

ρ is resistivity

L is length of wire

A is area

Thus, to decrease the resistance, we will have to use a shorter length and smaller area of wire.

8 0
2 years ago
a kickball is struck with a 15.2 m/s velocity at a 63.0 degree angle. it lands on a rooftop 2.40 s later. how high is the roof?​
Serhud [2]

Refer to the attachment

3 0
3 years ago
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