Energy and Its Conservation

Practice Test
      
  1.In Figure 8-2, if the radius of the CD is 6.0 cm and the angular velocity is 5.0 rad/s, what is the linear displacement of a point on the edge in 2.0 s?  
  a.   60 m  
  b.   3.8 m  
  c.   0.30 m  
  d.   0.60 m  
  Hint    
      
  2.The product of the force and the lever arm is called __________.  
  a.   torque  
  b.   equilibrium  
  c.   power  
  d.   range  
  Hint    
      
  3.A sled of mass 40.0 kg is pulled along flat, snow-covered ground. The static friction coefficient is 0.28, and the kinetic friction coefficient is 0.08. What force is needed to keep the sled moving at a constant velocity?  
  a.   3900 N  
  b.   31 N  
  c.   3.2 N  
  d.   310 N  
  Hint    
      
  4.The equation for calculating work when there is an angle between force and displacement is __________.  
  a.   W = Fd  
  b.   W = F/m  
  c.   W = FΔKE  
  d.   W = Fd cos θ  
  Hint    
      
  5.In Figure 8-2, if the radius of the CD is 6.0 cm and the angular velocity is 5.0 rad/s, what is its angular displacement in 2.0 s?  
  a.   0.60 rad  
  b.   6.0×101 rad  
  c.   1.7 rad  
  d.   1.0×101 rad  
  Hint    
      
  6.A sled of mass 40.0 kg is pulled along flat, snow-covered ground. The static friction coefficient is 0.28, and the kinetic friction coefficient is 0.08. What force will be needed to start the sled moving?  
  a.   31 N  
  b.   392 N  
  c.   110 N  
  d.   147 N  
  Hint    
      
  7.A 75-kg rock climber first climbs 25 m to the top of a quarry, then descends 75 m from the top to the bottom of the quarry. If the initial height is the reference level, what is the potential energy at the bottom?  
  a.   -3.7×104 J  
  b.   1.8×104 J  
  c.   3.7×104 J  
  d.   -5.5×104 J  
  Hint    
      
  8.The __________ of a machine is defined as the ratio of output work to input work.  
  a.   IMA  
  b.   efficiency  
  c.   mechanical advantage  
  d.   reliability  
  Hint    
      
  9.The centripetal acceleration is given by:  
  a.   ac = 2  
  b.   ac = ω2/r  
  c.   ac = r/ω  
  d.   ac =  
  Hint    
      
  10.The energy of an object resulting from motion is __________ energy.  
  a.   mechanical  
  b.   thermal  
  c.   potential  
  d.   kinetic  
  Hint    
      
  11.In Figure 9-4b, in which position does the diver have the largest moment of inertia?  
  a.   The third  
  b.   The fourth  
  c.   The last  
  d.   The second  
  Hint    
      
  12.A large chunk of ice with mass 12.0 kg falls from a roof 6.00 m above the ground. Ignoring air resistance, what is the kinetic energy of the ice when it reaches the ground?  
  a.   7.06×102 J  
  b.   -7.06×103 J  
  c.   -7.06×102 J  
  d.   7.06×103 J  
  Hint    
      
  13.The ratio of resistance force to effort force is called the __________.  
  a.   efficiency  
  b.   power  
  c.   torque  
  d.   mechanical advantage  
  Hint    
      
  14.When the net external force on a closed system is zero, it is described as __________.  
  a.   a normal system  
  b.   motionless  
  c.   an isolated system  
  d.   non-accelerating  
  Hint    
      
  15.A collision in which kinetic energy decreases is called a(n) __________.  
  a.   energy conservation  
  b.   mechanical collision  
  c.   inelastic collision  
  d.   elastic collision  
  Hint    
      
  16.The quantity of momentum used with objects rotating about a fixed axis is called __________.  
  a.   torque  
  b.   angular momentum  
  c.   uniform circular motion  
  d.   centripetal acceleration  
  Hint    
      
  17.You lift a 2.73-kg textbook from the floor to a shelf 1.75 m above the floor. What is the book's gravitational potential energy relative to the floor?  
  a.   14.3 J  
  b.   -46.8 J  
  c.   46.8 J  
  d.   93.1 J  
  Hint    
      
  18.Before a collision, a 35-kg object is moving at +10.0 m/s. Find the impulse that acted on the object if, after the collision, it moves at +8.0 m/s.  
  a.   -7.0×101 kg·m/s  
  b.   -2.8×102kg·m/s  
  c.   -7.0×102 kg·m/s  
  d.   7.0×101 kg·m/s  
  Hint    
      
  19.In Figure 8-5, if m1 = 1.0 g, m2 = 5.0 g, and r1 = 6.0 cm, what is r2?  
  a.   0.83 cm  
  b.   1.2 cm  
  c.   0.83 m  
  d.   1.2 m  
  Hint    
      
  20.What happens to an object when its velocity and angular velocity are zero or constant?  
  a.   It's in rotational equilbrium.  
  b.   It's in static equilibrium.  
  c.   It accelerates.  
  d.   It's in translational equilibrium.  
  Hint    

 
   
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