Momentum and Its Conservation

Practice Test
      
  1.The product of the average force and the time interval over which it acts is the __________.  
  a.   linear momentum  
  b.   acceleration  
  c.   velocity  
  d.   impulse  
  Hint    
      
  2.You are riding in a boat that is traveling 15.0 m/s in still water. You move from the bow to the stern at 3.0 m/s. What is your speed relative to the water?  
  a.   12.0 m/s relative to the water  
  b.   15.3 m/s relative to the water  
  c.   18.0 m/s relative to the water  
  d.   9.0 m/s relative to the water  
  Hint    
      
  3.Which of the following situations is physically the most like that depicted in Figure 6-9a?  
  a.   You step upwards on an upward-moving escalator.  
  b.   You jump up in an elevator that is going down.  
  c.   You walk toward the rear of a forward-moving train.  
  d.   You slide to the right on the seat of a forward-moving bus.  
  Hint    
      
  4.Two freight cars, each with a mass of 2.5×104 kg collide. One was initially moving at 3.7 m/s; the other was at rest. They stick together. What is their final speed?  
  a.   0.54 m/s  
  b.   3.7 m/s  
  c.   1.9 m/s  
  d.   2.4 m/s  
  Hint    
      
  5.In Figure 6-7, if the mass of the hammer is 7.26 kg, its center is 0.50 m from the thrower, and it is moving at a speed of 1.5 m/s, what is the force of the chain on the thrower's hands?  
  a.   33 N, inward  
  b.   22 N, outward  
  c.   22 N, inward  
  d.   33 N, outward  
  Hint    
      
  6.FΔt = mΔv is the equation for __________.  
  a.   net force  
  b.   angular momentum  
  c.   impulse-momentum  
  d.   linear momentum  
  Hint    
      
  7.A stone is thrown horizontally at 20 m/s from the top of a cliff 63 m high. How fast is it moving the instant before it hits the ground?  
  a.   29 m/s  
  b.   40 m/s  
  c.   33 m/s  
  d.   38 m/s  
  Hint    
      
  8.Two 1.00-kg masses have their centers 1.00 m apart. What is the force of attraction between them?  
  a.   6.67×1011 N  
  b.   9.7×10-8 N  
  c.   1.33×10-10 N  
  d.   6.67×10-11 N  
  Hint    
      
  9.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.   6.0×101 rad  
  b.   1.7 rad  
  c.   1.0×101 rad  
  d.   0.60 rad  
  Hint    
      
  10.A satellite orbits Earth 375 km above its surface. What is its speed in orbit?  
  a.   7.68 × 103 m/s  
  b.   7.61 × 103 m/s2  
  c.   7.61 × 103 m/s  
  d.   7.68 × 103 m/s2  
  Hint    
      
  11.When the net external force on a closed system is zero, it is described as __________.  
  a.   non-accelerating  
  b.   motionless  
  c.   a normal system  
  d.   an isolated system  
  Hint    
      
  12.In Newton's equation, F = Gm1m2/r2, r is __________.  
  a.   a universal constant  
  b.   the distance between a planet and the Sun  
  c.   the distance between the centers of the masses  
  d.   the difference in the two masses  
  Hint    
      
  13.If an object moves in a circle at steady speed it is in __________.  
  a.   torque  
  b.   equilibrium  
  c.   uniform circular motion  
  d.   projectile motion  
  Hint    
      
  14.Newton's laws are valid only __________.  
  a.   in rotating frames  
  b.   on Earth  
  c.   in vacuum  
  d.   in nonaccelerated or inertial frames  
  Hint    
      
  15.If you weigh 500.0 N on Earth's surface, how much would you weigh on the planet Jupiter? Jupiter has a mass of 1.90×1027 kg and a radius of 71.5×106 m.  
  a.   126 N  
  b.   1270 N  
  c.   1.26 N  
  d.   1.24×104 N  
  Hint    
      
  16.You accidentally throw your car keys horizontally at 5.0 m/s from a cliff 45 m high. How far from the base of the cliff should you look for your keys?  
  a.   45 m  
  b.   135 m  
  c.   225 m  
  d.   15 m  
  Hint    
      
  17.In Figure 8-5, if m1 = 1.0 g, m2 = 5.0 g, and r1 = 6.0 cm, what is r2?  
  a.   1.2 cm  
  b.   1.2 m  
  c.   0.83 cm  
  d.   0.83 m  
  Hint    
      
  18.In Figure 8-3, why does applying a force as in the picture at the top left result in no effect?  
  a.   The force is applied at the axis of rotation.  
  b.   The force is applied parallel to the lever arm.  
  c.   The force is applied perpendicular to the lever arm.  
  d.   The force is applied perpendicular to the axis of rotation.  
  Hint    
      
  19.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.   3.8 m  
  b.   60 m  
  c.   0.60 m  
  d.   0.30 m  
  Hint    
      
  20.An object is in __________ when the net torque exerted on it is zero.  
  a.   translational equilibrium  
  b.   rotational equilibrium  
  c.   static equilibrium  
  d.   equilibrium  
  Hint    

 
   
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