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
Softa [21]
3 years ago
13

A girl is sledding down a slope that is inclined at 30º with respect to the horizontal. The wind is aiding the motion by providi

ng a steady force of 148 N that is parallel to the motion of the sled. The combined mass of the girl and the sled is 75.7 kg, and the coefficient of kinetic friction between the snow and the runners of the sled is 0.299. How much time is required for the sled to travel down a 124-m slope, starting from rest?

Physics
1 answer:
lapo4ka [179]3 years ago
7 0

Answer:

 travel time is 7.58 s

Explanation:

We must know the acceleration of the sled and the girl, for this we must use Newton's second law

      F = m a

Since this is a vector equation, let's separate it into its xy components, the best selection of the coordinate system is the X axis parallel to the plane and the Y axis perpendicular to it.

In the attached you can see a free body diagram of this situation, let's write Newton's equations on each axis

X axis

      Wx + F - fr = m a            (1)

Axis y

     N- Wy = 0

     N = Wy

Let's use trigonometry to find the weight components

    Wx = W sin θ

    Wy = W cos θ

In addition, the formula for friction force is

    fr = n N

Let's clear the acceleration of equation 1

   

    a = (W sin θ + F - m N) / m

    a = (mg sin θ + F - m mg cos θ) / m

    a = g (sin θ -m cos θ) + F / m

Let's replace and calculate

    a = 9.8 (sin 30 - 0.299 cos 30) + 148 / 75.7

    a = 2.36 + 1.96

    a = 4,317 m / s²

We already have the acceleration, the speed is zero to leave the rest (Vo = 0) and give the length that runs 124 m, let's use the kinematic equations

   x = v₀ t + ½ a t²

   x = ½ a t²

   t² = 2x / a

  t = √ 2x / a

 

Let's calculate

  t = √( 2 124 / 4,317) = √ 57.45

  t = 7.58 s

You might be interested in
Three point charges are placed on the y-axis: a charge q at y=a, a charge –2q at the origin, and a charge q at y= –a. Such an ar
den301095 [7]

Answer:

electric field   Et = kq [1 / (x-a)² -2 / x² + 1 / (x+a)²]

Explanation:

The electric field is a vector, so it must be added as vectors, in this problem both the charges and the calculation point are on the same x-axis so we can work in a single dimension, remembering that the test charge is always positive whereby the direction of the field will depend on the load under analysis, if the field is positive, if the field is negative.

 a) Let's write the electric field for each charge and the total field

       E = k q /r

With k the Coulomb constant, q the charge and r the distance of the charge to the test point

       Et = E1 + E2 + E3

       E1 = k q / (x-a)²

       E2 = k (-2q) / x²  

       E3 = k q / (x + a)²

       Et = kq [1 / (x-a)² -2 / x² + 1 / (x+a)²]

The direction of the field is along the x axis

b) To use a binomial expansion we must have an expression the form (1-x)⁻ⁿ  where x << 1, for this we take factor like x from all the equations

       Et = kq/ x² [1 / (1-a/x)² - 2 + 1 / (1+a/x)²]

We use binomial expansion

     (1+x)⁻² = 1 -nx + n (n-1) 2! x² +… x << 1

     (1-x)⁻² = 1 +nx + n (n-1) 2! x² + ...

They replace in the total field and leaving only the first terms

       

   Et =kq/x² [-2 +(1 +2 a/x + 2 (2-1)/2 (a/x)² +…) + (1 -2 a/x + 2(2-1) /2 (a/x)² +.) ]

   Et = kq/x² [a²/x² + a²/x²2] = kq /x² [2 a²/x²]

Et = k q 2a²/x⁴

point charge

Et = k q 1/x²

Dipole

E = k q a/x³

3 0
2 years ago
Which units are used to express kinetic energy?
labwork [276]

Answer:

The SI units for energy is Joules.

4 0
3 years ago
Read 2 more answers
That is a difference between a law and a hypothesis?
telo118 [61]

Answer:

<em>A hypothesis</em> is a limited explanation of a phenomenon; a scientific theory is an in-depth explanation of the observed phenomenon.

<em> A law</em> is a statement about an observed phenomenon or a unifying concept, according to Kennesaw State University. ... However, Newton's law doesn't explain what gravity is, or how it works.

5 0
2 years ago
Anybody know these ?
pashok25 [27]

Answer:

1. a) 72 N.

2. a) 2 m/s².

Explanation:

Given the following data;

1. Mass = 90kg

Acceleration = 0.8 m/s²

To find the force;

Force = mass * acceleration

Force = 90 * 0.8

Force = 72 Newton.

2. Mass = 50kg

Force = 100N

To find the magnitude of acceleration;

Acceleration = force/mass

Acceleration = 100/50

Acceleration = 2 m/s²

5 0
2 years ago
The talk test can be used to measure the __________. A. knowledge of an activity B. intensity of an activity C. length of an act
marta [7]

Answer:

B.

Explanation:

According to CDC, if you’re doing moderate-intensity activity, you can talk but not sing during the activity.

8 0
3 years ago
Read 2 more answers
Other questions:
  • The high-speed winds around a tornado can drive projectiles into trees, building walls, and even metal traffic signs. In a labor
    7·1 answer
  • what might happen if an automobile manufacturer began making and selling cars based on a prototype that went through only one en
    10·1 answer
  • Joules are Nm, which is kg middot m^2/s^2 Use this relationship and 1 Btu = 1.0551 kJ to determine what Btu using primary Englis
    11·1 answer
  • This element has four valance electrons and four energy levels.
    9·1 answer
  • What examples can you din in your home tjat ate examples of kinetic and potential energy
    7·2 answers
  • A police officer uses a radar gun to determine the speed of a car. A specialized radar gun uses ultraviolet light to determine s
    15·1 answer
  • I am having trouble with writing a 2 paragraph summary about this vidio can someone help me
    5·1 answer
  • Five air-filled parallel-plate capacitors have the plate areas and plate separations listed below, where A and d are constants.
    12·1 answer
  • Someone please help me! Please help
    12·1 answer
  • HELP ME Please!!!!!!<br>Select ALL that apply
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!