All of the following are functions of the skeletal system EXCEPT:

A skateboarder with mass ms = 54 kg is standing at the top of a ramp which is hy = 3.3 m above the ground. The skateboarder then

Elan Coil [88]

Answer:

A) $W_{ff} =-744.12J$

B) $F_f=-W_{ff}*sin\theta /hy = 112.75N$

C) $F_{f2}=207.58N$

Explanation:

This question is incomplete. The full question was:

A skateboarder with mass ms = 54 kg is standing at the top of a ramp which is hy = 3.3 m above the ground. The skateboarder then jumps on his skateboard and descends down the ramp. His speed at the bottom of the ramp is vf = 6.2 m/s.

Part (a) Write an expression for the work, Wf, done by the friction force between the ramp and the skateboarder in terms of the variables given in the problem statement.

Part (b) The ramp makes an angle θ with the ground, where θ = 30°. Write an expression for the magnitude of the friction force, fr, between the ramp and the skateboarder.

Part (c) When the skateboarder reaches the bottom of the ramp, he continues moving with the speed vf onto a flat surface covered with grass. The friction between the grass and the skateboarder brings him to a complete stop after 5.00 m. Calculate the magnitude of the friction force, Fgrass in newtons, between the skateboarder and the grass.

For part A), we make a balance of energy to calculate the work done by the friction force:

$W_{ff}=\Delta E$

$W_{ff}=1/2*m*vf^2-m*g*hy$

$W_{ff}=-744.12J$

For part B), we use our previous value for the work:

$W_{ff}=-F_f*(hy/sin\theta)$ Solving for friction force:

$F_f=-W_{ff}*sin\theta /hy$

$F_f=112.75N$

For part C), we first calculate the acceleration by kinematics and then calculate the module of friction force by dynamics:

$Vf^2=Vo^2+2*a*d$

Solving for a:

$a=-3.844m/s^2$

Now, by dynamics:

$|F_f|=|m*a|$

$|F_f|=207.58N$

8 0

3 years ago

A rifle fires a 3.56 x 10-2-kg pellet straight upward, because the pellet rests on a compressed spring that is released when the

vivado [14]

Answer:

k = 773.64 N/m

Explanation:

Given:

mass of the pellet, m = 3.56 x 10² kg

Compression in spring, x = 6.61 × 10⁻² m

Height of rise of the pellet, h = 4.83 m

Now, let k be the spring constant

From the concept of conservation of energy, we get

gravitation potential energy acquired by the pellet will be from the energy provided by the spring

thus,

$mgh = \frac{1}{2}kx^2$

where, g is the acceleration due to the gravity

on substituting the values, we get

$3.56\times10^2\times9.8\times4.83 = \frac{1}{2}k\times(6.61\times10^{-2})^2$

or

1.685 = .002178 × k

k = 773.64 N/m

5 0

3 years ago

A father racing his son has 1/4 the kinetic energy of the son, who has 1/3 the mass of the father. The father speeds up by 1.2 m

sergejj [24]

Answer:

Explanation:

KE_s: Kinetic Energy Son

KE_f: Kinetic Energy Father.

Relationship

KE_f: = (1/4) KE_s

m_s: = (1/3) m_f

v_f: = velocity of father

v_s: = velocity of the son

Relationship

1/2 mf (v_f + 1.2)^2 = 1/2 m_s (v_s)^2 Multiply both sides by 2.

mf (v_f + 1.2)^2 = m_s * (v_s)^2 Substitute for the mass of the m_s

mf (v_f + 1.2)^2 = (m_f/3) * (v_s)^2 Divide both sides by father's mass

(v_f + 1.2)^2 = 1/3 * (v_s)^2 multiply both sides by 3

3*(v_f + 1.2)^2 = (v_s) ^2 Take the square root both sides

√3 * (v_f + 1.2) = v_s

Note

You should work your way through all the cancellations to find the last equation shown about
We have another step to go. We have to use the first relationship to get the final answer.

KE_f = (1/4) KE_s Multiply by 4

4* KE_f = KE_s Substitute (again)

4*(1/2) m_f (v_f + 1.2)^2 = 1/2* (1/3)m_f *v_s^2 Divide by m_f

2* (v_f + 1.2)^2 = 1/6 * (v_s)^2 multiply by 6

12*(vf + 1.2)^2 = (v_s)^2 Take the square root

2*√(3* (v_f + 1.2)^2) = √(v_s^2)

2*√3 * (vf + 1.2) = v_s

Use the second relationship to substitute for v_s so you can solve for v_f

2*√3 * ( v_f + 1.2) = √3 * (v_f + 1.2) Divide by sqrt(3)

2(v_f + 1.2) = vf + 1.2

Edit

2vf + 2.4 = vf + 1.2

2vf - vf + 2.4 = 1.2

vf = 1.2 - 2.4

vf = - 1.2

This answer is not possible, but 2 of us are getting the same answer. The other person is someone whose math I would never question. She rarely makes an error. And I do mean rarely. Could you check to see that you have copied this correctly?

5 0

4 years ago

Which chemicals are major contributors to ozone layer destruction? Select two answer choices.

Nastasia [14]

Answer:

what are the answers to select? or do you just say them

Explanation:

???

3 0

3 years ago

Read 2 more answers

Cho đoạn thẳng OAB. Đặt điện tích q tại O thì cường độ điện trường do nó gây ra ở A là EA =1600V/m,tạiBlàEB =100V/m.Cường độ điệ

BlackZzzverrR [31]

Answer:.

Explanation:

8 0

3 years ago