[領域]    大一普物�                           (題目相關領域)

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[題目]

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Exercises

1. A 2.5-kg object falls vertically downward in a viscous medium at a constant speed of 2.5 m/s. How much work is done by the force the viscous medium exerts on the object as it falls 80 cm?

A. +2.0 J       B. +20 J        C. –2.0 J      D. –20 J       E. +40 J

2.  A  3.0-kg  block  is  on  a  horizontal  surface.  The  block  is  at  rest  when,  at  t  =  0,  a  force (magnitude  P  =  12  N)  acting  parallel  to  the  surface  is  applied  to  the  block  causing  it  to accelerate. The coefficient of kinetic friction between the block and the surface is 0.20. At what rate is the force P doing work on the block at t = 2.0 s?

A. 54 W B. 49 W C. 44 W D. 59 W E. 24 W

3.  A  20-kg  block  on  a  horizontal  surface  is  attached  to  a  light  spring  (force  constant  =  8.0 kN/m). The block is pulled 10 cm to the right from its equilibrium position and released from  rest.  When  the  block  has  moved  2.0  cm  toward  its  equilibrium  position,  its  kinetic energy is 13 J. How much work is done by the frictional force on the block as it moves the
2.0 cm?

A. –2.5 J      B. –1.4 J      C. –3.0 J      D. –1.9 J      E. –14 J

4. A 10-kg block on a rough horizontal surface is attached to a light spring (force constant =
1.4  kN/m).  The  block  is  pulled  8.0  cm  to  the  right  from  its  equilibrium  position  and released from rest. The frictional force between the block and surface has a magnitude of 30
N. What is the kinetic energy of the block as it passes through its equilibrium position?

A. 4.5 J        B. 2.1 J        C. 6.9 J        D. 6.6 J        E. 4.9 J


5. A single conservative force Fx  = (6.0x – 12) N (x is in m) acts on a particle moving along the x axis. The potential energy associated with this force is assigned a value of +20 J at x = 0. What is the potential energy at x = 3.0 m?

A. +11 J        B. +29 J        C. +9.0 J       D. –9.0 J      E. +20 J


6. A 0.80-kg object tied to the end of a 2.0-m string swings as a pendulum. At the lowest point
of its swing, the object has a kinetic energy of 10 J. Determine the speed of the object at the instant when the string makes an angle of 50° with the vertical.

A. 5.6 m/s      B. 4.4 m/s      C. 3.3 m/s      D. 5.0 m/s      E. 6.1 m/s

7. A spring (k = 600 N/m) is placed in a vertical position with its lower end supported by a horizontal surface. A 2.0-kg block that is initially 0.40 m above the upper end of the spring
is dropped from rest onto the spring. What is the kinetic energy of the block at the instant it has fallen 0.50 m (compressing the spring 0.10 m)?

A. 5.3 J        B. 6.8 J        C. 6.3 J        D. 5.8 J        E. 6.5 J
1

8. A 2.0-kg block sliding on a rough horizontal surface is attached to one end of a horizontal spring  (k  =  250  N/m)  which  has  its  other  end  fixed.  The  block  passes  through  the equilibrium position with a speed of 2.6 m/s and first comes to rest at a displacement of
0.20 m from equilibrium. What is the coefficient of kinetic friction between the block and the horizontal surface?

A. 0.32 B. 0.45 C. 0.58 D. 0.19 E. 0.26

9.  A  2000-kg  truck  traveling  at  a  speed  of  6.0  m/s  makes  a  90°  turn  in  a  time  of  4.0  s  and emerges  from  this  turn  with  a  speed  of  4.0  m/s.  What  is  the  magnitude  of  the  average resultant force on the truck during this turn?

A. 4.0 kN       B. 5.0 kN       C. 3.6 kN       D. 6.4 kN       E. 0.67 kN

10. A 3.0-kg ball with an initial velocity of (4i + 3j) m/s collides with a wall and rebounds with
a velocity of (–4i + 3j) m/s. What is the impulse exerted on the ball by the wall?

A. +24i N s     B. –24i N s    C. +18j N s     D. –18j N s    E. +8.0i N s

11. A 2.0-kg object moving 5.0 m/s collides with and sticks to an 8.0-kg object initially at rest.
Determine the kinetic energy lost by the system as a result of this collision.

A. 20 J B. 15 J C. 30 J D. 25 J E. 5.0 J


12.  A  3.0-kg  mass  sliding  on  a  frictionless  surface  has  a  velocity  of  5.0  m/s  east  when  it undergoes  a  one-dimensional  inelastic  collision  with  a  2.0-kg  mass  that  has  an  initial velocity of 2.0 m/s west. After the collision the 3.0-kg mass has a velocity of 1.0 m/s east. How much kinetic energy does the two-mass system lose during the collision?

A. 22 J B. 24 J C. 26 J D. 20 J E. 28 J

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