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3 years ago

Nicholas sends 20.0 minutes ironing shirts with his 1800-watt irn . How many joules of energy were usedby the iron

1 answer:

6 0

1 watt = 1 joule/sec
1800 watts = 1800 joules/sec

   (1800 J/sec) x (20 min) x (60 sec/min)

   = (1800 x 20 x 60) joules = 2,160,000 joules .

   ( 2.16 megajoules )

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A ball is thrown straight down with a speed of Va2.00 from a building 40.00 meters high. How much S time passes before the ball

-Dominant- [34]

Answer:

Option C is the correct answer.

Explanation:

Considering vertical motion of ball:-

Initial velocity, u = 2 m/s

Acceleration , a = 9.81 m/s²

Displacement, s = 40 m

We have equation of motion s= ut + 0.5 at²

Substituting

s= ut + 0.5 at²

40 = 2 x t + 0.5 x 9.81 x t²

4.9t² + 2t - 40 = 0

t = 2.66 s or t = -3.06 s

So, time is 2.66 s.

Option C is the correct answer.

6 0

3 years ago

A toy train is pushed forward and released at Xi = 4.0 m with a speed of 2.5 m/s. It rolls at a steady speed for 2.0 s, then one

Fittoniya [83]

I don't think that 4m has anything to do with the problem. anyway. here. A___________________B_______C where A is the point that the train was released. B is where the wheel started to stick C is where it stopped From A to B, v=2.5m/s, it takes 2s to go A to B so t=2 AB= v*t = 2.5 * 2 = 5m The train comes to a stop 7.7 m from the point at which it was released so AC=7.7m then BC= AC-AB = 7.7-5 = 2.7m now consider BC v^2=u^2+2as where u is initial speed, in this case is 2.5m/s v is final speed, train stop at C so final speed=0, so v=0 a is acceleration s is displacement, which is BC=2.7m substitute all the number into equation, we have 0^2 = 2.5^2 + 2*a*2.7 0 = 6.25 + 5.4a a = -6.25/5.4 = -1.157 so acceleration is -1.157m/(s^2)

8 0

3 years ago

Read 2 more answers

g The electric power needs of a community are to be met by windmills with 40-m-diameter rotors. The windmills are to be located

Ksenya-84 [330]

Answer:

Explanation:

Given Data

The diameter of the wind mills is d = 40m

Velocity of the air is V = 6 m / s

Required power output is: P ₀ = 2100 k W

Expression to calculate the exergy of the air is

E = V ² / 2

Substitute the value in above expression

E = ( 6 m / s ) ² / 2

E = 18 m ² / s ² x (1kJ/kg / 1000m²/s²)

E = 0.018 k J / k g

Expression to calculate the density of the air is

P v =m R T

m /v = P /RT ⋯ ⋯( I )

Here

m is the mass of the air,

v is the volume of the air,

P is the atmospheric pressure,

T is the standard temperature at the atmospheric pressure and

R is the gas constant

As the density is

ρ = m /V

Substitute the value in expression (I)

ρ = 101 kP a /( 0.287 k J / k g ⋅ K ) ( 298 K )

ρ = 1.180 k g / m ²

Expression to calculate the mass flow rate is

m = ρ A V ⋯ ⋯ ( I I )

Here A is the area of the windmill

Expression to calculate the A is

A = π /4 d ²

Substitute the value in above expression

A = π /4 ( 40 m ²)

A = 1256.63 m ²

Substitute the value in expression (II)

m = ( 1.180 k g / m ³) ( 1256.63 m ²) ( 6 m / s )

m = 8896.94 k g / s

Expression to calculate the maximum power available to the windmill is

P w = m ( V ² /2 )

Substitute the value in above expression

P w = 8896.94 k g / s ( (6m/s)²/2 )

P w = 160144.92 W × ( 1 W /1000 k W )

P w = 160.144 k W

Expression to calculate the number of windmills required is

n = P o /P w

Substitute the value in above expression

n=2100kw/160.144kw

n=13.11

8 0

3 years ago

Which of these is a mixture?

PSYCHO15rus [73]

Answer:

Air is a mixture.

Explanation:

Air is a homogeneous mixture. It is made up of gaseous substances such as nitrogen, oxygen, and smaller amounts of others.

Carbon dioxide is a pure substance, not a mixture.

Carbon is another pure substance, it cannot be separated into other substances.

Oxygen is just oxygen, it does not contain any other substance.

5 0

3 years ago

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Which factors affect gravitational potential force but not elastic potential energy

Inga [223]

Answer:

The mass of the object involved and the value of the gravitational acceleration

Explanation:

- Gravitational potential energy is defined as the energy possessed by an object in a gravitational field due to its position with respect to the ground:

$U=mgh$

where m is the mass of the object, g is the gravitational acceleration and h is the heigth of the object with respect to the ground.

- Elastic potential energy is defined as the energy possessed by an elastic object and it is given as:

$U=\frac{1}{2}kx^2$

where k is the spring constant of the elastic object, while x is the compression/stretching of the spring with respect to the equilibrium position.

As we can see from the equations, both types of energy depends on the relative position of the object/end of the spring with respect to a certain reference position (h in the first formula, x in the second formula), but gravitational potential energy also depends on m (the mass) and g (the gravitational acceleration) while the elastic energy does not.

3 0

3 years ago

Read 2 more answers