F=ma problems

Ex. 5B of M1 book:

Q15) A horizontal force of 2N is just sufficient to prevent a block of mass 1kg from sliding down a plane inclined at arcsin 7/25 to the horizontal. Find the coefficient of friction between the block and the plane and the acceleration with which the block will move when the force is removed.

18) A block of mass 1.6kg is placed on a rough plane inclined at 45 degrees to the horizontal. The coefficient of friction between the block and the plane is 1/4. Model the block as a particle and hence find the acceleration of the block down the plane. Find the velocity of the block after 2 seconds, assuming that it starts from rest.

I'd really appreciate it if someone could help me with these questions!

Reply 1

dvs

10

What have you tried?

Note for the first one that the 2N force is actually horizontal, so you will have to resolve it before using it.

Reply 2

investor

lost_hamster

Ex. 5B of M1 book:

Q15) A horizontal force of 2N is just sufficient to prevent a block of mass 1kg from sliding down a plane inclined at arcsin 7/25 to the horizontal. Find the coefficient of friction between the block and the plane and the acceleration with which the block will move when the force is removed.

R= perpendicular force so

R=1x9.8cos16.3+2sin16.3=9.97
F=1x9.8sin16.3-2cos16.3=0.831
so F=uR
U=0.0833

not sure about the acceleration it doesnt seem to be working for me :frown:

18) A block of mass 1.6kg is placed on a rough plane inclined at 45 degrees to the horizontal. The coefficient of friction between the block and the plane is 1/4. Model the block as a particle and hence find the acceleration of the block down the plane. Find the velocity of the block after 2 seconds, assuming that it starts from rest.

I'd really appreciate it if someone could help me with these questions!

R=1.6x9.8cos45x0.25=2.77
F=1.6x9.8sin45=11.1
F-uR=1.6a
11.1-2.77=1.6a
a=5.2

v=u+at
v=0+2x5.2=10.4

F=ma problems

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