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
Andre45 [30]
3 years ago
13

A cross-country skier slides horizontally along the snow and comes to rest after sliding a distance of 11 m. If the coefficient

of kinetic friction between her skis and the snow is μk = 0.020, determine her speed at the start of the slide.
Physics
2 answers:
Basile [38]3 years ago
6 0

Answer:

v_o = 4.54 m/s  

Explanation:

<u>Knowns  </u>

From equation, the work done on an object by a constant force F is given by:  

W = (F cos Ф)S                                   (1)  

Where S is the displacement and Ф is the angle between the force and the displacement.  

From equation, the kinetic energy of an object of mass m moving with velocity v is given by:  

K.E=1/2m*v^2                                       (2)

From The work- energy theorem , the net work done W on an object equals the difference between the initial and the find kinetic energy of that object:  

W = K.E_f-K.E_o                                 (3)

<u>Given </u>

The displacement that the sled undergoes before coming to rest is s = 11.0 m and the coefficient of the kinetic friction between the sled and the snow is μ_k = 0.020  

<u>Calculations</u>

We know that the kinetic friction force is given by:

f_k=μ_k*N

And we can get the normal force N by applying Newton's second law to the sled along the vertical direction, where there is no acceleration along this direction, so we get:  

∑F_y=N-mg

     N=mg

Thus, the kinetic friction force is:  

f_k = μ_k*N  

Since the friction force is always acting in the opposite direction to the motion, the angle between the force and the displacement is Ф = 180°.  

Now, we substitute f_k and Ф into equation (1), so we get the work done by the friction force:  

W_f=(f_k*cos(180) s

      =-μ_k*mg*s

Since the sled eventually comes to rest, K.E_f= 0 So, from equation (3), the net work done on the sled is:  

W= -K.E_o    

Since the kinetic friction force is the only force acting on the sled, so the net work on the sled is that of the kinetic friction force  

W_f= -K.E_o  

From equation (2), the work done by the friction force in terms of the initial speed is:  

W_f=-1/2m*v^2  

Now, we substitute for W_f= -μ_k*mg*s, and solving for v_o so we get:  

-μ_k*mg*s = -1/2m*v^2  

v_o = √ 2μ_kg*s

Finally, we plug our values for s and μ_k, so we get:  

v_o = √2 x (0.020) x (9.8 m/s^2) x (11.0 m) = 4.54 m/s  

v_o = 4.54 m/s  

lyudmila [28]3 years ago
3 0
<h2>Answer:</h2>

2.10m/s

<h2>Explanation:</h2>

Here, we use the work-energy principle that states that the work done (W) on a body is equal to the change in kinetic energy (ΔK_{E}) of the body. i.e

W = ΔK_{E}        [ΔK_{E} = K_{E}₂ - K_{E}₁]

=> W = K_{E}₂ - K_{E}₁           ----------------(i)

[K_{E}₂ = final kinetic energy K_{E}₁ = initial kinetic energy]

But;

W = F x s cos θ

Where;

F = net force acting on the body

s = displacement of the body due to the force

θ = angle between the force and the displacement.

Also;

K_{E}₂ = \frac{1}{2} x m x v²

K_{E}₁ = \frac{1}{2} x m x u²

Where;

m = mass of the body

v = final velocity of the body

u = initial velocity of the body

Substitute the values of K_{E}₂ , K_{E}₁ and W into equation (i) as follows;

F x s cos θ =  (\frac{1}{2} x m x v²) - (\frac{1}{2} x m x u²)    -----------------(ii)

From the question;

i. The skier comes to a rest, this implies that the final velocity (v) of the body(skier) is 0.

Therefore substitute v = 0 into equation (ii) to get;

F x s cos θ =  (\frac{1}{2} x m x 0²) - (\frac{1}{2} x m x u²)

F x s cos θ =  0 - (\frac{1}{2} x m x u²)

F x s cos θ =   - (\frac{1}{2} x m x u²)             ---------------------(iii)

ii. Since there is no motion in the vertical direction, the net force (F) acting is the kinetic frictional force (F_{R}) in the horizontal direction

i.e F = F_{R}

But we know that the frictional force F_{R}, is given by;

F = F_{R} = μk x N

Where;

μk = coefficient of static friction

N = Normal reaction which is equal to the weight (m x g) of the skier [since there is no motion in the vertical]

=> F =  F_{R}  = μk x m x g          [m = mass of the skier and g = acceleration due to gravity]

iii. Also, since the only force acting is the frictional force acting to oppose motion, the angle θ between the force and the displacement is 180°

iv. Now substitute all of these values into equation (iii) as follows;

F x s cos θ =   - (\frac{1}{2} x m x u²)

μk x m x g x s cos θ = -  (\frac{1}{2} x m x u²)

<em>Divide through by m;</em>

μk x g x s cos θ = -  (\frac{1}{2} x u²)        ----------------(iv)

<em>From the question;</em>

s = 11m

μk = 0.020

Take g = 10m/s²

θ = 180°

<em>Substitute these values into equation (iv) and solve for u;</em>

0.020 x 10 x 11 cos 180 = -  (\frac{1}{2} x u²)

0.020 x 10 x 11 x (-1) = -  (\frac{1}{2} x u²)

-2.2 = -  \frac{1}{2} x u²

u² = 4.4

u = \sqrt{4.4}

u = 2.10m/s

Therefore, the speed of the skier at the start of the slide is 2.10m/s

You might be interested in
How many turns are in its secondary coil, if its input voltage is 120 V and the primary coil has 210 turns
Tasya [4]

Complete Question

How many turns are in its secondary coil, if its input voltage is 120 V and the primary coil has 210 turns.

The output from the secondary coil is  12 V

Answer:

The value  is  N_s  =  21 \  turns

Explanation:

From the equation we are told that

   The input voltage is  V_{in}  = 120 \ V

   The number of turns of the primary coil is N_p =  210 \  turn

    The output from the secondary is V_o =  12V

From the transformer equation

   \frac{N_p}{V_{in}}  =\frac{N_s}{V_o}

Here N_s is the number of turns in the secondary coil

=> N_s  =  \frac{N_p}{V_{in}}  *  V_s

=>N_s  =  \frac{210}{120}  *  12

=>N_s  =  21 \  turns

4 0
3 years ago
HELPPPPPPP PLEASE!!! does anybody have the answer key to edge. physics lab report : mechanical equivalent to heat? one page of d
Karo-lina-s [1.5K]

Answer:

the mechanical equivalent of heat states that motion and heat are mutually interchangeable and that in every case

Explanation:

6 0
3 years ago
Read 2 more answers
In regions where few species existed before or where species were wiped out what occurs?
marysya [2.9K]
I cant really say but i believe it is called extinction
5 0
3 years ago
A roller coaster takes energy to make the first rise, but then it should be able to run the course of the track without any inpu
den301095 [7]
I would say that this is the first law of thermodynamics.
6 0
3 years ago
Read 2 more answers
Light with a wavelength of 400 nm strikes the surface of cesium in a photocell, and the maximum kinetic energy of the electrons
Firdavs [7]

Answer:

The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.

Explanation:

Given that,

Wavelength = 400 nm

Energy E=1.54\times10^{-19}\ J

We need to calculate the longest wavelength of light that is capable of ejecting electrons from that metal

Using formula of energy

E = \dfrac{hc}{\lambda}

\lambda=\dfrac{hc}{E}

Put the value into the formula

\lambda=\dfrac{6.63\times10^{-34}\times3\times10^{8}}{1.54\times10^{-19}}

\lambda=1292\times10^{-9}\ m

\lambda=1292\ nm

Hence, The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.

8 0
3 years ago
Other questions:
  • Tire or false
    12·1 answer
  • The sun is going down and most of the land is dark but we still can see silhouettes and outlines of objects because some light i
    8·2 answers
  • A woman can row a boat at 5.60 km/h in still water. (a) If she is crossing a river where the current is 2.80 km/h, in what direc
    15·2 answers
  • What is the application of physics<br>​
    12·1 answer
  • A circular saw blade with a radius of 0.145 m starts from rest and turns in a vertical plane with a constant angular acceleratio
    10·1 answer
  • How are mathematics and science related?
    11·1 answer
  • Do all of our scientific instruments have a limit on how precise they can make a measurement?
    14·1 answer
  • Where is the sun located in the galaxy?
    10·2 answers
  • What is the velocity of a wave that has a frequency of 200 Hz and a<br> wavelength of 0.5m?
    15·1 answer
  • PLZ PLZ PLZ PLZ PLZ PLZ PLZ HELPPPPPPPPPPPPPPPPP
    14·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!