1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
RideAnS [48]
3 years ago
7

A 2-kg block slides along a rough horizontal surface and slows to 10 m/s after traveling 20 m. If the kinetic coefficient of fri

ction between the block and surface is 0.2, the initial speed (m/s) of the block was most nearly:
Physics
1 answer:
bagirrra123 [75]3 years ago
3 0

Answer:

initial speed is 13.36 m/s

Explanation:

given data

mass = 2 kg

velocity = 10 m/s

distance = 20 m

friction= 0.2

to find out

initial speed

solution

we find first friction force that is

friction force = friction ×mass×g    ...........1

put here value

friction force = 0.2 × 2 × 9.81  

friction force = 3.924 N

here a will be -ve due to friction

- friction force = mass × acceleration

acceleration = - friction force / mass

acceleration = - 3.924 / 2  

acceleration = - 1.962 m/s²

and we know velocity formula that is  

V² = V(i)² + 2as

put here value

10² = V(i)² + 2(-1.962)(20)

V(i) = 13.36  

so initial speed is 13.36 m/s

You might be interested in
EXTREME HELP!!!!
mrs_skeptik [129]

the anwser is c is always the best anwser


8 0
3 years ago
Having difficulty finding the PE and KE for these values no mass is given. Does anyone know to go solve these?
Alexandra [31]

11) 1.04\cdot 10^7 J

12) 1.04\cdot 10^7 J

13) 50.0 m/s

14) 41.6 m/s

Explanation:

11)

The potential energy of an object is the energy possessed by the object due to its position relative to the ground. It is given by

PE=mgh

where

m is the mass of the object

g is the acceleration due to gravity

h is the height relative to the ground

Here in this problem, when the train is at the top, we have:

m = 8325 kg (mass of the train + riders)

g=9.8 m/s^2 (acceleration due to gravity)

h = 127 m (height of the train at the top)

Substituting,

PE=(8325)(9.8)(127)=1.04\cdot 10^7 J

12)

According to the law of conservation of energy, the total mechanical energy of the train must be conserved (in absence of friction). So we can write:

KE_t + PE_t = KE_b + PE_b

where

KE_t is the kinetic energy at the top

PE_t is the potential energy at the top

KE_b is the kinetic energy at the bottom

PE_b is the potential energy at the bottom

The kinetic energy is the energy due to motion; since the train is at rest at the top, we have

KE_t=0

Also, at the bottom the height is zero, so the potential energy is zero

PE_b=0

Therefore, we find:

KE_b=PE_t=1.04\cdot 10^7 J

13)

The kinetic energy of an object is the energy of the object due to its motion. Mathematically, it is given by

KE=\frac{1}{2}mv^2

where

m is the mass of the object

v is the speed of the object

From question 12), we know that the kinetic energy of the train at the bottom is

KE=1.04\cdot 10^7 J

We also know that the mass is

m = 8325 kg

Therefore, we can calculate the speed of the train at the bottom:

v=\sqrt{\frac{2KE}{m}}=\sqrt{\frac{2(1.04\cdot 10^7)}{8325}}=50.0 m/s

14)

At the top of the second hill, the total mechanical energy of the train is still conserved.

Therefore, we can write again:

KE_1 + PE_1 = KE_2 + PE_2

where

KE_1 is the kinetic energy at the top of the 1st hill

PE_1 is the potential energy at the top of the 1st hill

KE_2 is the kinetic energy at the top of the 2nd hill

PE_2 is the potential energy at the top of the 2nd hill

From the previous questions, we know that

KE_1=0

and

PE_1=1.04\cdot 10^7 J

The height of the second hill is

h = 39 m

So we can also find the potential energy at the second hill:

PE_2=mgh=(8325)(9.8)(39)=3.2\cdot 10^6 J

So, the kinetic energy at the second hill is

KE_2=PE_1-PE_2=1.04\cdot 10^7 - 3.2\cdot 10^6 =7.2\cdot 10^6 J

And so, the speed is

v=\sqrt{\frac{2KE_2}{m}}=\sqrt{\frac{2(7.2\cdot 10^6)}{8325}}=41.6 m/s

4 0
2 years ago
The first law of thermodynamics states that energy can neither be created nor destroyed. If this is true then why are we always
riadik2000 [5.3K]

Answer:

The second law of thermodynamics states in an isolated system, the entropy (the amount of thermal energy that cannot be converted into mechanical work, also known as the amount of disorder) always increases, therefore, an isolated system always require an external input (new sources) of energy for there to be orderliness or for the available energy of the system to remain constant or increase

Explanation:

5 0
2 years ago
Alexandra is attempting to drag her 32.6 kg golden retriever across the wooden floor by applying a horizontal force. What force
vichka [17]

Answer:

230.26 N

Explanation:

Since the speed is constant, acceleration is zero hence the net force will be given by the product of mass, coefficient of friction and acceleration due to gravity

F=0.72*32.6*9.81=230.26 N

7 0
3 years ago
Points A, B, and C form the vertices of a triangle in a nonuniform electrostatic field. The electrostatic work done on a particl
Trava [24]

Answer:

Explanation:

Let electric potential at A ,B and C be Va , Vb and Vc respectively.

Work done = charge x potential difference

Wab = q ( Va - Vb )

Wac =  q (  Va -  Vc )

Given

Wac = - Wab / 3

3Wac = - Wab

Now

Wbc = q ( Vb - Vc )

= q [ ( Va-Vc ) - ( Va - Vb )]  

= Wac - Wab

= Wac + 3Wac

= 4Wac

4 0
2 years ago
Other questions:
  • A submarine sends a signal and receives an echo after 5 seconds. Calculate the speed of sound if distance of object from submari
    15·2 answers
  • Please help me answer this question! Will appreciate help very much. a) Draw a circuit to show 3 lights in series b) Draw a circ
    7·1 answer
  • What are the constant parameters in Charles' gas law?
    15·1 answer
  • What can you conclude about the total mechanical energy of a pendulum as it swings back and forth?
    10·1 answer
  • A subway train is traveling at 22.2 m/s when it approaches a slower train 50m ahead traveling in the same direction at 6.94 m/s.
    10·1 answer
  • Ana vive a 3 km del instituto y María en la misma carretera, 500 m. Más lejos. Todas las mañanas, a las ocho y cuarto, cogen la
    6·1 answer
  • PLEASE HELP ME THIS IS VERY IMPORTANT!!!!!!!!!!!!! 20 points and I will give brainlyest
    6·2 answers
  • A mercury in barometer shows a height of 70cm.What height would be shown in the barometer at the same place if water density 1.0
    15·1 answer
  • Mention the importance of occupation??​
    14·1 answer
  • Rory uses a force of 25 N to lift her grocery bag while doing 50 J of work. How far did she lift the
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!