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3 years ago

15

Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/a in 20 s. What is te net force acting on the body?

1 answer:

Strike441 [17]3 years ago

5 0

The guy below is wrong!

F=ma
Where force = mass x acceleration

We dont have acceleration, a= change in velocity divided by the time taken.
a = v (final velocity) - u (initial) / t
a us 8-0 (at rest means u was 0) / 20 = 0.4

Using F=ma

F= mass x acceleration
F= 4 x 0.4
F=1.6 N

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True

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3 years ago

1. When the mass of the ice added to the cup increases, the amount of thermal energy needed to change the temperature of the ice

Paha777 [63]

1. When the mass of the ice added to the cup increases, the amount of thermal energy needed to change the temperature of the ice decreases or increases

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3. If the mass of ice added to the cup increases, the total energy in the cup will decrease or increase1. When the mass of the ice added to the cup increases, the amount of thermal energy needed to change the temperature of the ice decreases or increases

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Total kinetic energy of the water

Average kinetic energy of the water

Total amount of heat in the water

3. If the mass of ice added to the cup increases, the total energy in the cup will decrease or increase1. When the mass of the ice added to the cup increases, the amount of thermal energy needed to change the temperature of the ice decreases or increases

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Total kinetic energy of the water

Average kinetic energy of the water

Total amount of heat in the water

3. If the mass of ice added to the cup increases, the total energy in the cup will decrease or increase1. When the mass of the ice added to the cup increases, the amount of thermal energy needed to change the temperature of the ice decreases or increases

2. When the students measure the temperature of the water in the cups during the investigation, what is it the students are measuring?

Total kinetic energy of the water

Average kinetic energy of the water

Total amount of heat in the water

3. If the mass of ice added to the cup increases, the total energy in the cup will decrease or increase1. When the mass of the ice added to the cup increases, the amount of thermal energy needed to change the temperature of the ice decreases or increases

2. When the students measure the temperature of the water in the cups during the investigation, what is it the students are measuring?

Total kinetic energy of the water

Average kinetic energy of the water

Total amount of heat in the water

3. If the mass of ice added to the cup increases, the total energy in the cup will decrease or increase

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3 years ago

A box is placed on a 30o frictionless incline. What is the acceleration of the box as it slides down the incline

balandron [24]

Answer:

<em>2.78m/s²</em>

Explanation:

Complete question:

<em>A box is placed on a 30° frictionless incline. What is the acceleration of the box as it slides down the incline when the co-efficient of friction is 0.25?</em>

According to Newton's second law of motion:

$\sum F_x = ma_x\\F_m - F_f = ma_x\\mgsin\theta - \mu mg cos\theta = ma_x\\gsin\theta - \mu g cos\theta = a_x\\$

Where:

$\mu$ is the coefficient of friction

g is the acceleration due to gravity

Fm is the moving force acting on the body

Ff is the frictional force

m is the mass of the box

a is the acceleration'

Given

$\theta = 30^0\\\mu = 0.25\\g = 9.8m/s^2$

Required

acceleration of the box

Substitute the given parameters into the resulting expression above:

Recall that:

$gsin\theta - \mu g cos\theta = a_x\\$

9.8sin30 - 0.25(9.8)cos30 = ax

9.8(0.5) - 0.25(9.8)(0.866) = ax

4.9 - 2.1217 = ax

ax = 2.78m/s²

<em>Hence the acceleration of the box as it slides down the incline is 2.78m/s²</em>

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3 years ago

(a) As a soap bubble thins it becomes dark, because the path length difference becomes small compared with the wavelength of lig

OLga [1]

Answer:

t< 75 nm

Explanation:

A soap bubble is a thin film where when the beam enters the film it has a 180º phase change due to the refractive index and the wavelength changes between

λ = λ₀ / n

In the case of constructive interference in the curve of the spherical film it is

2 nt = (m + ½) λ₀

Where t is the thickness of the film and n the refractive index that does not indicate that we use that of water n = 1.33, m is an integer. The thickness of the film for the first interference (m = 0) is

t = λ₀ / 4 n

A thickness less than this gives destructive interference.

Let's look for the thickness for the visible spectrum

Violet light λ₀ = 400 nm = 400 10⁻⁹ m

t₁ = 400 10⁻⁹ / 4 1.33

t₁ = 75.2 10-9 m

Red light λ₀ = 700 nm = 700 10⁻⁹ m

t₂ = 700 10⁻⁹ / 4 1.33

t₂ = 131.6 10⁻⁹ m

Therefore, for all wavelengths to have destructive interference, the thickness must be less than 75 10⁻⁹ m = 75 nm

b) a film like eta is very thin, it is achieved when gravity thins the pomp, but any movement or burst of air breaks it,

3 0

3 years ago