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3 years ago

You are using a constant force to speed up a toy car from an initial speed of 6.5 m/s

Physics

1 answer:

Pachacha [2.7K]3 years ago

7 0

By the work-energy theorem, the total work done on the car is equal to the change in its kinetic energy:

W = ∆K

W = 1/2 (0.34 kg) (22.9 m/s)² - 1/2 (0.34 kg) (6.5 m/s)²

W ≈ 82 J

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A bullet has a mass of 8 grams and a muzzle velocity of 340m/sec. A baseball has a mass of 0.2kg and is thrown by the pitcher at

Thepotemich [5.8K]

Answer:

Momentum of bullet

$P = 2.72 kg m/s$

momentum of baseball

$P = 8 kg m/s$

Explanation:

As we know that momentum is defined as the product of mass and velocity

here we know that

mass of the bullet = 8 gram

velocity of bullet = 340 m/s

momentum of the bullet is given as

$P = mv$

$P = (\frac{8}{1000})(340)$

$P = 2.72 kg m/s$

Now we have

mass of baseball = 0.2 kg

velocity of baseball = 40 m/s[/tex]

momentum of baseball is given as

$P = (0.2)(40)$

$P = 8 kg m/s$

3 0

4 years ago

Air expands isentropically from 2.2 MPa and 77°C to 0.4 MPa. Calculate the ratio of the initial to the final speed of sound.

djyliett [7]

Answer:

The ratio of initial to final speed of sound is given as 1.28.

Explanation:

As per the thermodynamic relation of isentropic expansion

$\frac{T_2}{T_1}=(\frac{P_2}{P_1})^{\frac{k-1}{k}}$

Here

$P_1$ is the pressure at point 1 which is given as 2.2 MPa
$T_1$ is the temperature at point 1 which is given as 77 °C or 273+77=350K

$P_2$ is the pressure at point 1 which is given as 0.4 MPa
$T_2$ is the temperature at point 2 which is to be calculated
k is the ratio of specific heats given as 1.4

Substituting values in the equation

$\frac{T_2}{350}=(\frac{0.4}{2.2})^{\frac{1.4-1}{1.4}}\\\frac{T_2}{350}=(0.18)^{0.2857}\\T_2=(0.18)^{0.2857} \times 350 \\T_2=0.61266 \times 350\\T_2=214.43 K$

As speed of sound c is given as

$c=\sqrt{kRT}$

for initial to final values it is given as

$\frac{c_i}{c_f}=\frac{\sqrt{k_1R_1T_1}}{\sqrt{k_2R_2T_2}}$

As values of k and R is constant so the ratio is given as

$\frac{c_i}{c_f}=\sqrt{\frac{T_1}{T_2}}$

Substituting values give

$\frac{c_i}{c_f}=\sqrt{\frac{350}{214.43}}\\\frac{c_i}{c_f}=\sqrt{1.63}}\\\frac{c_i}{c_f}=1.277 \approx 1.28$

So the ratio of initial to final speed of sound is 1.28.

5 0

3 years ago

A material having an index of refraction of 1.35 is used as an antireflective coating on a piece of glass (n = 1.50). What shoul

exis [7]

Answer:

103.70 nm

Explanation:

The minimum thickness of the film is given by $t=\frac{\lambda }{4n}$ where $\lambda$ is the wavelength and n is the index of the refraction

We have n =1.35

Wavelength $\lambda =560nm$

So the minimum thickness of the film $t=\frac{\lambda }{4n}=\frac{560}{4\times 1.35}=103.70\ nm$

3 0

3 years ago

An electric water heater consumes 2.5 kW for 1.9 h per day.

Alecsey [184]

Answer:

The cost of running the electric water heater for one year is 55.2391 $

Explanation:

The simple rule of 3 helps to quickly solve proportionality problems when you have three known values and one unknown. If two quantities are directly proportional (that is, when multiplying or dividing one of them by a number, the other is multiplied or divided respectively by the same number) the rule of three can be applied as follows:

a ⇒ b

c ⇒ x

So: $x=\frac{c*b}{a}$

where a, b and c are the known values and x is the value you want to find out.

In this case, you can first apply the following rule of three: if 2.5 kW are consumed in 1.9 hours, in 1 hour how many kW are consumed?

$kWh=\frac{1 h*2.5 kW}{1.9 h}$

kWh=1.316

So an electric water heater consumes 1.316 kWh in one day. You apply another simple rule of three: if the heater in 1 day consumes 1.316 kWh, in 365 days (1 year) how many kWh are consumed?

$kWh=\frac{365 days*1.316 kWh}{1 day}$

kWh= 480.34

So an electric water heater consumes 480.34 kWh in a year.

If 1 kWh costs 11.5 cents, 480.34 kWh how many cents does it cost?

$cost=\frac{480.34 kWh*11.5 cents}{1 kWh}$

cost= 5,523.91 cents

Finally, if 100 cents is equal to 1 dollar, 5,523.91 cents, how many dollars are equal?

$cost=\frac{5,5523.91 cents*1 dollar}{100 cents}$

cost= 55.2391 $

The cost of running the electric water heater for one year is 55.2391 $

5 0

3 years ago

Someone pls help me !!!!

Mekhanik [1.2K]

It’s d. The time it takes for the water to boil. It is adding different amounts of salt to see which one will boil quicker if adding an amount of salt.

5 0

3 years ago

Read 2 more answers