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Troyanec [42]
3 years ago
14

if a sports car can go from 0 to 60 mph in 3.8 seconds, what would be it's final speed after 6 seconds if it's starting speed wa

s 30.0 mph?
Physics
1 answer:
erma4kov [3.2K]3 years ago
4 0
Verrrrrry interesting !

Acceleration = (change in speed) / (time for the change)

The car's acceleration is  (60 mph) / (3.8 sec)  = (60/3.8)  mile/hr-sec .

Final speed = (original speed)  +  (acceleration · time)

                 = (30 mi/hr)  +  (60/3.8  mi/hr-sec)·(6 sec)

                 = (30)mi/hr  +  (360 / 3.8)mi/hr

                 =      124.7 mph .
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How do motors use energy? Do they convert electrical energy into mechanical energy OR mechanical energy into electrical energy?
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Answer:

Motors convert electrical energy into mechanical energy

Explanation:

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A laser pulse of duration 25 ms has a total energy of 1.4 J. The wavelength of this radiation is
SpyIntel [72]

Answer:

n = 4 x 10¹⁸ photons

Explanation:

First, we will calculate the energy of one photon in the radiation:

E = \frac{hc}{\lambda}\\\\

where,

E = Energy of one photon = ?

h = Plank's Constant = 6.625 x 10⁻³⁴ J.s

c = speed of light = 3 x 10⁸ m/s

λ = wavelength of radiation = 567 nm = 5.67 x 10⁻⁷ m

Therefore,

E = \frac{(6.625\ x\ 10^{-34}\ J.s)(3\ x\ 10^8\ m/s)}{5.67\ x\ 10^{-7}\ m}

E = 3.505 x 10⁻¹⁹ J

Now, the number of photons to make up the total energy can be calculated as follows:

Total\ Energy = nE\\1.4\ J = n(3.505\ x\ 10^{-19}\ J)\\n = \frac{1.4\ J}{3.505\ x\ 10^{-19}\ J}\\

<u>n = 4 x 10¹⁸ photons</u>

8 0
3 years ago
You observe three carts moving to the left. Cart A moves to the left at nearly constant speed. Cart B moves to the left, gradual
Lady bird [3.3K]

Answer:cart B

Explanation:

For cart A speed is constant therefore there is no acceleration because acceleration is rate of change of velocity

thus there is no net force

For cart B there is change in velocity in the left direction , so there is net acceleration towards left

Force=mass\times acceleration

so there is net force in the left direction

For cart C there is decrease in velocity i.e. negative acceleration or deceleration . Therefore there is a net force towards right which opposes the motion                

6 0
2 years ago
A fireperson is 50 m from a burning building and directs a stream of water from a fire hose at an angle of 300 above the horizon
notsponge [240]

Answer:

We can think the water stream as a solid object that is fired.

The distance between the fireperson and the building is 50m. (i consider that the position of the fireperson is our position = 0)

The angle is 30 above the horizontal. (yo wrote 300, but this has no sense because 300° implies that he is pointing to the ground).

The initial speed of the stream is 40m/s.

First, using the fact that:

x = R*cos(θ)

y = R*sin(θ)

in this case R = 40m/s and θ = 30°

We can use the above relation to find the components of the velocity:

Vx = 40m/s*cos(30°) = 34.64m/s

Vy = 20m/s.

First step:

We want to find the time needed to the stream to hit the buildin.

The horizontal speed is 34.64m/s and the distance to the wall is 50m

So we want that:

34.64m/s*t = 50m

t = 50m/(34.64m/s) = 1.44 seconds.

Now we need to calculate the height of the stream at t = 1.44s

Second step:

The only force acting on the water is the gravitational one, so the acceleration of the stream is:

a(t) = -g.

g = -9.8m/s^2

For the speed, we integrate over time and we get:

v(t) = -g*t + v0

where v0 is the initial speed: v0 = 20m/s.

The velocity equation is:

v(t) = -g*t + 20m/s.

For the position, we integrate again over time:

p(t) = -(1/2)*g*t^2 + 20m/s*t + p0

p0 is the initial height of the stream, this data is not known.

Now, the height at the time t = 1.44s is

p(1.44s) = -5.9m/s^2*(1.44s)^2 + 20m/s*1.44s + po

             = 16.57m + p0

So the height at wich the stream hits the building is 16.57 meters above the initial height of the fire hose.

5 0
3 years ago
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