7.4 m = _________________________ mm 7.4x 10-3 74 7.4 x 103 7.4 x 104

Does the number of particles change as the substance changes its state?

Leviafan [203]

Particles stay the same unless there is a chemical change whether the matter is solid, liquid or gas. ... When substances change state there is no change in mass so if 100 g of ice is melted 100g of water are formed this will boil to form 100g of steam (this is called "conservation of mass").

4 0

3 years ago

A 62-kg person jumps from a window to a fire net 20.0 m directly below, which stretches the net 1.4 m. Assume that the net behav

gayaneshka [121]

Answer:

a) x = 0.098

b) x = 2.72 m

Explanation:

(a) To find the stretch of the fire net when the same person is lying in it, you can assume that the net is like a spring with constant spring k. It is necessary to find k.

When the person is falling down he acquires a kinetic energy K, this energy is equal to the elastic potential energy of the net when it is max stretched.

Then, you have:

$K=U\\\\\frac{1}{2}mv^2=\frac{1}{2}kx^2$ (1)

m: mass of the person = 62kg

k: spring constant = ?

v: velocity of the person just when he touches the fire net = ?

x: elongation of the fire net = 1.4 m

Before the calculation of the spring constant, you calculate the final velocity of the person by using the following formula:

$v^2=v_o^2+2gy$

vo: initial velocity = 0 m/s

g: gravitational acceleration = 9.8 m/s^2

y: height from the person jumps = 20.0m

$v=\sqrt{2gy}=\sqrt{2(9.8m/s^2)(20.0m)}=14\frac{m}{s}$

With this value you can find the spring constant k from the equation (1):

$mv^2=kx^2\\\\k=\frac{mv^2}{x^2}=\frac{(62kg)(14m/s)^2}{(1.4m)^2}=6200\frac{N}{m}$

When the person is lying on the fire net the weight of the person is equal to the elastic force of the fire net:

$W=F_e\\\\mg=kx$

you solve the last expression for x:

$x=\frac{mg}{k}=\frac{(62kg)(9.8m/s^2)}{6200N/m}=0.098m$

When the person is lying on the fire net the elongation of the fire net is 0.098m

b) To find how much would the net stretch, If the person jumps from 38 m, you first calculate the final velocity of the person again:

$v=\sqrt{2gy}=\sqrt{2(9.8m/s^2)(38m)}=27.29\frac{m}{s}$

Next, you calculate x from the equation (1):

$x=\sqrt{\frac{mv^2}{k}}=\sqrt{\frac{(62kg)(27.29m/s)^2}{6200N/m}}\\\\x=2.72m$

The net fire is stretched 2.72 m

5 0

3 years ago

Help with 7,8,9 please!!

Marysya12 [62]

# 7 the answer is 4) because you need opposites in order to attract

# 8 I'm going to guess it is 4) because electricity is needed in order a light bolt to work.(don't take my word for this one I'm not sure but, the other answer are correct)

# 9 the answer is 4) because the comb dose collect negative charges from the hair in order to make the hair have positive charge.

Hope this helped : )

4 0

3 years ago

Which equation represents mass-energy equivalence? E = m2c E = mc2 E = (mc)2 E = mc

motikmotik

Einstein's energy mass equivalence relation say that if the whole given mass is converted to energy then it would be

$E = mc^2$

where

m = mass in kg

c = speed of light in m/s

this is the origination of quantum physics and by this formula we can relate the dual nature of light and particle

So correct relation above will be

$E = mc^2$

4 0

3 years ago

Read 2 more answers

Why might it be important to know your inherited traits passed down by your parents?

ExtremeBDS [4]

Answer:

health factors that could harm you or your offspring

3 0

3 years ago