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Determining magnitudes of forces on a block

  1. Mar 3, 2009 #1
    A block of mass (2.20kg) is pushed 2.21m along a frictionless horizontal table by a constant 19.5 N force directed 26.4 deg below the horizontal.

    I have found the work done by the applied force, which is 3.86 J

    I got stuck after that...I still need help figuring out the following questions

    If someone could help show me how to setup my equations, I should be able to get them

    1. Determine the magnitude of the normal force exerted by the table.

    2. Determine the magnitude of the force of gravity.

    3. Determine the net force on the block.
  2. jcsd
  3. Mar 4, 2009 #2
    How good are you with vector addition and subtraction?

    For the first question, your are pushing 'down' by an amount, and 'along' by and amount. If these two amounts were added as vectors (i.e. with magnitudes w/ directions) they would give you the 19.5N at 26.4 deg below the horiz.

    So the amount you are pushing down is
    19.5 *sin(26.4)= F(down)

    then the force from gravity is

    F(g)= m*g= 2.2 *10=22N

    So both of these two forces (you and from grav.) push down on the table, therefore the table pushes back by the same amount, namely the magnitude of the normal force exerted by the table
  4. Mar 4, 2009 #3
    I am not that strong at adding vectors.

    Now that I got both of these forces, do I just add Fn and Fg together to get the net force?
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