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11.1 Example 1

A block of 3 kilograms of mass is above of 30 degrees inclined plane. If it leave the rest and there isn’t friction, Which is the velocity of the block after travelled 2 meters? Which is its acceleration?

Solution with FisicaLab

Select the Dynamic group and, inside this, the Particles module. Erase the content of the chalkboard and select the SI system. And add one element Oblique force, one element Block above an inclined plane to the right and one element Stationary reference system, to make the free body diagram of the block. As show the image below: The element Stationary reference system write to default the gravity value, but the time data is unknown:

g

9.81

t

t

Now, to the element Block above an inclined plane to the right, write:

Name

Block

m

3

ang

30

a

a

vi

0

vf

vf

d

-2

Relative to

sf

The sign of the travelled distance is negative (remember the reference system to these elements). To the element Oblique force write:

f

n

ang

60

If the plane is inclined 30 degrees, the normal force is inclined 60 degrees. Now click in the icon Solve to get the answer:

a = -4.905 m/s2 ;  vf = -4.429 m/s ;  t = 0.903 s ;
n = 25.487 N ;
Status = success.

The relevant data are vf = -4.426 m/s and a = -4.905 m/s2, both with negative sign (remember the reference system to these elements).

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