What is the average speed of this car over the entire journey ?

Hey everyone! THIS IS VERY IMPORTANT!!!!!!!! im in 8th grade and my science DBA is tomorrow and i need dba notes. its lesson 4.

Anvisha [2.4K]

Answer:

look on quizlet! there are tons of study sets to choose from that probably are In your curriculum!

Explanation:

question/answer

What are two types of chemical weathering?

Oxidation and acids

What are some physical forces?

Wind, water, plants, pressure change, ice

There are two types of weathering

Mechanical and chemical

Weathering is the breakdown of

Rock at or near the Earth's surface.

What are three things that rocks can tell you about?

How the earth is moving, how old it is, and about events of the past.

Minerals are

The building blocks of rocks.

What are three things about minerals?

They occur naturally, almost all of them are solid, and they are in organic-not formed from living material.

Magma is

Molten rock from the mantle layer of the Earth.

When magma cools or hardens, it is called

Igneous rock.

When magma reaches the Earth's surface as lava and then cools and hardens into rock, it is called an

Extrusive rock.

5 0

2 years ago

Our atmosphere constantly being heated by the sun is an example of

grin007 [14]

I believe this is an example of radiation because the sun will warm up the ground, trees, atmosphere, etc; thus, the sun would "radiate" heat.

5 0

3 years ago

A box moving on a horizontal surface with an initial velocity of 20 m/s slows to a stop over a time period of 5.0 seconds due so

egoroff_w [7]

Answer:

μ= 0.408 : coefficient of kinetic friction

Explanation:

Kinematic equation for the box:

$a=\frac{v_{f} -v_{i} }{t}$ Formula( 1)

a= acceleration

v_i= initial speed =0

v_f= final speed= 20 m/s

t= time= 5 s

We replace data in the formula (1):

$a=\frac{0-20}{5}$

$a= -\frac{20}{5}$

a= - 4m/s²

Box kinetics: We apply Newton's laws in x-y:

∑Fx=ma : second law of Newton

-Ff= ma Equation (1)

Ff is the friction force

Ff=μ*N Equation (2)

μ is the coefficient of kinetic friction

N is the normal force

Normal force calculation

∑Fy=0 : Newton's first law

N-W=0 W is the weight of the box

N=W= m*g : m is the mass of the box and g is the acceleration due to gravity

N=9.8*m

We replace N=9.8m in the equation (2)

Ff=μ*9.8*m

Coefficient of kinetic friction ( μ) calculation

We replace Ff=μ*9.8*m and a= -4m/s² in the equation (1):

-μ*9.8*m: -m*4 : We divide by -m on both sides of the equation

9.8*μ=4

μ=4 ÷ 9.8

μ= 0.408

8 0

3 years ago

Six dogs pull a two-person sled with a total mass of 220 kg. The coefficient of kinetic friction between the sled and the snow i

irina [24]

Answer:

a) 2457J

b) 558W

c) 337N

Explanation:

Assuming dogs started from rest.

$v=a*t\\t=\frac{a}{v}\\v=12\frac{km}{h}\frac{1000m}{km}*\frac{1h}{3600s}\\\\v=3.3m/s\\\\t=\frac{3.3m/s}{0.75m/s^2}\\t=4.4s$

and the displacement is given by:

$d=\frac{1}{2}*a*t^2\\d=7.3m$

Using the energy conservation formula:

$K_i+U_i+W_d+W_f=K_f+U_f$

Because the motion started from rest the initial kinetic energy is zero, the motion occurred in-ground level so the gravitational energy is zero too.

the work done by the friction force is given by:

$W_f=F_f*d*cos(\theta)\\W_f=\µ*m*g*d*cos(180)\\W_f=0.08*220kg*9.8m/s^2*7.3m*(-1)\\W_f=-1259J$

so:

$W_d=\frac{1}{2}*220kg*(3.3m/s)^2+1259J\\W_d=2457J$

The power is given by:

$P=\frac{W}{t}\\\\P=\frac{2457J}{4.4s}\\\\P=558W$

and the force exerted by the dogs:

$W_d=F_d*d*cos(\theta)\\F_d=\frac{W_d}{d*cos(0)}\\\\F=\frac{2457J}{7.3m*(1)}\\\\F=337N$

4 0

3 years ago

The product PV, where P and V represent pressure and volume respectively, is a unit for which?

Basile [38]

<span>PV is actually energy. P = F/A force per area, and V = A L, so PV = F L and force times distance is work which is energy. If you have P in N/m^2 and V in m^3, you have Joules, N-m.</span>

6 0

3 years ago