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1. A tension force of 3.25 N acts horizontally on a 5.00 kg block. The block accelerates at 0.890 m/s2. What is the force of kinetic friction?

 

 

 

 

2. The 60 kg student on skates pushes a 55 kg student on skates. The 55 kg student accelerates at 2.5 m/s2. What is the acceleration of the 60 kg student?

 

 

 

3. A 0.160 kg ice puck collides with a 0.180 kg ice puck. Both were originally moving at the same speed. Which one has the larger change in velocity?

 

 

4.A 6.0 kg block of ice rests on a surface that is tilted by θ=12°. Find the acceleration of the block, ignoring any friction.

 Dec 10, 2019

Best Answer 

 #1
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1.    Remember f= ma ?

           the force net on the object is 3.25 one direction and kinetic frictional force in the OPPOSITE direction

                (3.25 - K) = 5 kg  .890 m/s2        Solve for K

 

2.   Same thing here   f=ma 

         I THINK what they mean is 'equal and opposite reactions'   and conservation of energy etc

             f = ma    for the 55 kg student

                 = 55 kg (2.5 m/s2)     This force will also act BUT in the opposite direction for the 60 kg student

                    55 (2.5) = 60 kg a     Solve for a

 

3.   conservation of momentum

         Think about a large truck hitting a smaller car....which will have the biggest change in velocity ???

 

4. You must find the force acting DOWN the plane (NOT the NORMAL force.....we are ignoring friction))

       then    f = ma   

 Dec 11, 2019
 #3
avatar+21725 
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1    (3.25 - K) = 5 kg  .890 m/s2        Solve for K

      3.25 - k = 5 (.890)

       3.25-k = 4.45

           k = -1.2 N

 

2 yes

3 yes

4  mg sin 12  is the force down-plane

    f= mg sin 12 = ma

        g sin 12 = a =2.04 m/s2     (this should make you realize that the acceleration is not dependent on the mass of the object)

 Dec 11, 2019
 #4
avatar+1656 
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im still kind of unsure how you solved the last one (4)? what did you multiply or divide?

jjennylove  Dec 11, 2019
edited by jjennylove  Dec 11, 2019
 #5
avatar+21725 
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mg sin 12  is the force down-plane

    f= mg sin 12 = ma       (divide both sides by 'm')

 

        g sin 12 = a

      9.81  *  sin 12  = a

       9.81 * .20791 =a

  a =2.04 m/s2   

ElectricPavlov  Dec 11, 2019

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