Adquisición de conocimiento, de Aplicación, de Metacognición y Actividad Integradora

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Application Activity

[pic 21]

Phase 2

A) A space probe is conducted to the outer space by a rocket, but once placed in orbit the rocket is detached. What keeps the probe moving after the rocket no longer holds it?

By the force of gravity

B) If you are standing on a skateboard at rest, on a smooth surface, when you begin to walk on the skateboard, it slides back. Explain this situation in terms of Newton's first law.

An object that is parked will remain at rest unless some external force acts on it.

C) If you are inside a resting car that is hit in the back, you could suffer what is called a whiplash. How can this session be explained in terms of Newton's first law?

What is a force acting on the car

D) Regarding the previous question, how does the headrest of the seat in your car help the neck in a collision behind?

Helps cushion the blow

E) A hockey disc slides on ice with constant speed, is the disc in balance? Why? Justify your answer.

If due to its constant speed

F) The force of gravity pulls down a book that sits on a table, what force prevents the book from accelerating down?

The strength of the table

G) When you stand, does the soil have a force on you? How much force does it have? Why does not that force lift you off the ground?

If, my weight, is a stationary force

H) We currently know that the earth spins at more than 100,000 km per hour around the sun, however we do not feel it. Why? How would you explain Newton's laws in this situation?

We do not feel it because it is a turning on itself

I) When a ball is thrown upwards, it stops momentarily at the top of its trajectory, is it in equilibrium at that moment? Why?

Yes, because when it reaches its maximum point it does not rotate with non-uniform velocity.

phase 3.

Problem

Free-Body diagram

Procedure and solution

A 350kg car is waiting for the green light to continue What force does it need to generate so the car reaches a speed of 60km / hr in 10 seconds

M=350 km 60km/h= 16.7m/s

Vo=0 a=f/m

V= 60km/h a= 6.7 km/h/10s

T= 10s a= 1.67 m/s

F= ma

F= (350km)(1.67km/h)

F= 585 n

A block of 10kg slides horizontally 6km by applying an F = 70N at 30 °. Disregarding the frictional force calculates the acceleration of the box.

F= 70n Fx=ma

= 30° 70cos30=60.62[pic 22]

M=10kg a= 60.62/10 =6.06 m/s

Fy=ma

Fy+N-w=0

N=(10)(9.8)= -70sen30°

N=63 N

A 23kg block slides horizontally 12m by applying an F = 170N at 50 °. Calculate the acceleration of the box and the floor is 0.43

M=23 kg Fy=0

F=170 n N+fy-w=0

=50° 170sen50-23kg(9.8)=0[pic 23]

W=.43 N=94

X=12m

Fx=ma

170cos50-40.2N=23

A= 68.8/23 =2.99 m/s

A 15kg box slides on a 40 ° inclined plane with the horizontal at constant speed. Calculate the coefficient of friction between the box and the surface.

m= 15kg wx-f=0 N= (15) (9.8)

Ncos-sen N= 147cos40[pic 24][pic 25][pic 26]

N= .839 N= 12.60N

F=mg/cos F= 191.89N[pic 27]

F= 147/ .7666

Calculate the force required to raise a 50kg box by a 30 ° slope with the horizontal, if the coefficient of friction between the box and the surface is 0.25.

M=15kg Fx= ma

= 30 F= mg-f=0[pic 28]

Cf=.25 F=mg+f

F=N F= 290 + 106.08 =596.08 N

(.25)(424.35)

W=106.08N N=(50) (9.8)

N= 490cos30° = 424.35

It calculates the tension and the force that is generated when holding the poster of 16kg of weight in the following arrangement

M=16kg Fx= ma T1senw[pic 29]

= 50° F=Tcos T1= [pic 30][pic 31][pic 32]

F= 204.68cos50° T1= [pic 33]

F= 131.56N T1= 204.68

It calculates the tension 1 and 2 that generate in the cords when holding the poster of 16kg of weight in the following arrangement

M= 16kg T2= T1cos T1= [pic 34][pic 35]

=10° T2= 243.93cos 40° T1= 243.93 N[pic 36]

T2= 186.86

Integrating Activity

This activity consists of 2 phases in which we shall put the practice the acquired knowledge from the theme of translational balance.

Phase1