Which of the following are not units used to measure energy?

A ball is launched from ground level and hits the ground again after an elapsed time of 4 seconds and after traveling a horizont

jeka94

Answer:

1)a. It is constant the whole time the ball is in free-fall.

2)b. = 14 m/s

3) e. = 19.6 m/s

Explanation:

1) given that the only force acting on the ball is gravity, gravity acts along the vertical axis. Since no other force acts on the ball then the horizontal velocity will remain constant all through the flight since there is no horizontal force acting on the ball.

2) speed = distance/time

horizontal distance = 56m

Time = 4 seconds

Speed = 56m/4s = 14m/s

3) acceleration due to gravity g = 9.8m/s^2

Initial vertical velocity = u

Final vertical velocity = v = -u

Using the law of motion;

v = u + at

a = acceleration = -g = -9.8m/s^2

t = time of flight = 4

Substituting the values;

-u = u - 4(9.8)

-2u = -4(9.8)

u = -4(9.8)/-2

u = 2(9.8) = 19.6 m/s

Initial vertical velocity = u = 19.6 m/s

3 0

3 years ago

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

Nikolas had an idea that he could use the compressed carbon dioxide in a fire extinguisher to propel him on his skateboard.

Vikentia [17]

The Newton’s law Nikolas would use to come up with this idea is the Third law that states:

When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

So, in this case, let's name the first Body A which is the skateboard and the second body B which is the compressed carbon dioxide in a fire extinguisher. Then, as shown in the figure below, according to the Third law:

 $FA = -FB$

8 0

3 years ago

Read 2 more answers

A person sitting in a chair with wheels stands up, causing the chair to roll backward across the floor. How would you describe t

OleMash [197]

Scenes the chair wheels are up the person is rolling backwards and if the wheels were down then the person would go forwards

3 0

3 years ago

Why is it correct to say that solar energy, wind energy, and some forms of water power have the same source?

Inessa [10]

Maybe because all of them come from natural elements (sun, air and water)

8 0

3 years ago