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BurstBullet:
Hello!

These are a few questions regarding the Dynamics of Moving Particles:

1) A force of 20N is applied at an angle of 60(degrees) to the horizontal to a mass of 4kg on a smooth horizontal table. What is the acceleration of the mass? ans: 2.5ms-2

2) A mass of 2kg is at rest on a rough horizontal table. A force of 20N is applied to the mass, the force making an angle of 30(degrees) with the table. Frictional resistance is equal to 5N. What is the acceleration of the mass? ans: 6.2 ms-2

3) A coin can slife on a horizontal table. The coefficient of friction is 1/3. The coin is projected along the table with intial speed of 2ms-1. Find the time before the coin comes to rest. ans: 0.6s


I'd appreciate any help.. thanks in advance!

A.T:
1.As surface is smooth there would be no friction. Hence Fr=0N
First find horizontal component of force:-
F=20cos60=10N
As F=ma
a=F/m
a=10/4=2.5 ms-2

2.Fr=5N
D=Horizontal component of force(Driving force)
D=20cos30
Using D-Fr=ma
20cos30 - 5 =2a
a=6.16 ms-2

3. Fr=(U)N      (U)=Mew or whatever u call it (cofficient of friction) :P
N=mg
Fr=(U)N
ma=(U)mg
cancel m on both sides
a=(U)g
a=1/3 * 10
a= 10/3 ms-2

a is the deceleration produced, hence we will take it as '-'ve

a=(v-u)/t
-10/3 = (0-2)/t
t=0.6 sec


Feel free to ask any more question, or any thing u didnt understand from above.  ;)

7ooD:
thx A.t that waz great welcomez to the forum dude +rep for u  ;D

BurstBullet:
Thanks A.T! That was really helpful!

A.T:
No Problem. ;)

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