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Hatshy
3 months ago
10

A 55 kg gymnast wedges himself between two closely spaced vertical walls by pressing his hands and feet against the walls. Part

a what is the magnitude of the friction force on each hand and foot? Assume they are all equal.
Physics
1 answer:
ValentinkaMS [3.4K]3 months ago
5 0

answer:

Let frictional forces due to both hands and feets be "Ff" each(since its given that they all are equal), acting in upward direction( in opposite direction of supposed motion).\\
Then since there is no motion of gymnast thus net frictional force due to both hands and feets will be exactly balanced by the weight of the gymnast,\\ i.e\\
4f_{f}=weight =mg\\
f_{f}=\frac{55x9.8}{4}\\
=134.75N

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The parasailing system shown uses a winch to pull the rider in towards the boat, which is traveling with a constant velocity. Du
ValentinkaMS [3465]

Answer:

The force magnitude is  F_{net}= 1.837 *10^4N

and it is directed at 57.98° from the horizontal in a counterclockwise manner.

Explanation:

The problem states that

At t = 0, \theta = 20^o

The angular rate of increase is w = 2 \ ^o/s

Converting to revolutions per second gives us  \theta ' = 2 \ ^o/s * \frac{\pi}{180} =0.0349\ rps

The rope length is defined by

                      r = 125- \frac{1}{3}t^{\frac{3}{2} }    

    At \theta =30^o, Tension T of the rope is 18 kN.

     The weight of the para-sailor is M_p = 75kg

In analyzing the question, we observe that the equation for length can be represented as a linear displacement equation.

 The derivative of displacement results in velocity.

Hence,

           r' = -\frac{1}{3} [\frac{3}{2} ] t^{\frac{1}{2} }

signifies the velocity, and further differentiation yields acceleration.

Therefore,

         r'' = -\frac{1}{4} t^{-\frac{1}{2} }

Now considering the moment when the rope forms a 30° angle with the water,

typically angular velocity is expressed as

                      w = \frac{\Delta \theta}{\Delta t}

where \theta represents the angular displacement.

Next, evaluating the interval from 20^o \ to \ 30^o gives us

                 2 = \frac{30 -20 }{t -0}

making t the focal point.

             t = \frac{10}{2}

               = 5s

At this time, the displacement measures

             r = 125- \frac{1}{3}(5)^{\frac{3}{2} }  

                = 121.273 m

The linear velocity computes to

             r' = -\frac{1}{3} [\frac{3}{2} ] (5)^{\frac{1}{2} }

                = -1.118 m/s

Whereas linear acceleration calculates as

          r'' = -\frac{1}{4} (5)^{-\frac{1}{2} }

              = -0.112m/s^2

Generally, radial acceleration is given by

         \alpha _R = r'' -r \theta'^2

              = -0.112 - (121.273)[0.0349]^2

              = 0.271 m/s^2

Simultaneously, angular acceleration can be represented as

                 \alpha_t = r \theta'' + 2 r' \theta '

Then \theta '' = \frac{d (0.0349)}{dt} = 0

Thus,

             \alpha _t = 121.273 * 0 + 2 * (-1.118)(0.0349)

                   = -0.07805 m/s^2

The resultant acceleration is mathematically denoted as

                a = \sqrt{\alpha_R^2 + \alpha_t^2 }

                  = \sqrt{(-0.07805)^2 +(-0.027)^2}

                  = 0.272 m/s^2

Now the acceleration's direction is mathematically expressed as

                  tan \theta_a = \frac{\alpha_R }{\alpha_t }

                       \theta_a = tan^{-1} \frac{-0.271}{-0.07805}

                           = 73.26^o

               

The y-axis force acting on the para-sailor is mathematically shown as

               F_y = mg + Tsin 30^o + ma sin(90- \theta )

                    = (75 * 9.8) + (18 *10^3) sin 30 + (75 * 0.272)sin(90-73.26)

                    = 9.74*10^3 N

The x-axis force acting on the para-sailor is represented as

              F_x = mg + Tcos 30^o + ma cos(90- \theta )    

             = (75 * 9.8) + (18 *10^3) cos 30 + (75 * 0.272)cos(90-73.26)

             = 1.557 *10^4 N

The overall force is calculated as

                      F_{net} = \sqrt{F_x^2 + F_y^2}

                             =\sqrt{(1.557 *10^4)^2 + (9.74*10^3)^2}

                            F_{net}= 1.837 *10^4N

The directional force is evaluated as

              tan \theta_f = \frac{F_y}{F_x}

                   \theta_f = tan^{-1} [\frac{1.557*10^4}{9.74*10^3} ]

                       = tan^{-1} (1.599)

                       = 57.98^o

     

                     

7 0
3 months ago
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