4. 4.A 86-kg mass is pulled along a frictionless surface by a force F such that

Question

4.4.A 86-kg mass is pulled along a frictionless surface by a force F such that its acceleration is6 m/s2. A 3-kg mass slides along the top of the 86-kg mass and has an acceleration of 35 m/s2.(It thus slide back relative to the 86-kg mass). What is the frictional force in newtons exerted by the 86-kg mass on the 3-kg mass?

5.A woman holding a 13-kg block by a cord designed to withstand a tension of 164 N steps into an elevator. When the elevartor starts up, the cord breaks. What was the minimum acceleration (in m/s2) of the elevator?

6. 6.Two bodies of mass m1= 5 kg and m2 = 9 kg are in contact and rest on a horizontal frictionless table. A horizontal force of 9 N is applied to m1. What is the contact force in newtons between m1 and m2?

Explanation / Answer

4.Force=m(a2-a1)=3(35-6)=87N

5.m(g+a)=164.Hence g+a=164/13=12.61

a=12.61-9.8=2.81m/s^2

6.F=(m1+m2)*a

9=(5+9)a

a=9/14

Force between them=Force on m2=9*9/14=81/14=5.79

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