Work–energy theorem Knowledge-Based Download PDF

Questions

1. 1.

   A net work of -36 J is done on an object moving along a horizontal path, reducing its kinetic energy to one-fourth of its initial value. What was the initial kinetic energy of the object?

   • A) 27 J
   • B) 48 J
   • C) 12 J
   • D) 144 J
2. 2.

   Two blocks of masses $m$ and $4m$ are initially at rest on a frictionless horizontal surface. If identical constant net forces act on both blocks over the same displacement, what is the ratio of the final speed of the block of mass $m$ to that of the block of mass $4m$?

   • A) $1 : 4$
   • B) $1 : 2$
   • C) $2 : 1$
   • D) $4 : 1$
3. 3.

   A net work $W$ is required to accelerate an object from rest to a speed $v$ along a frictionless horizontal surface. According to the work–energy theorem, how much additional net work must be done on the object to increase its speed from $v$ to $2v$?

   • A) $W$
   • B) $3W$
   • C) $4W$
   • D) $2W$
4. 4.

   A constant net force does 96 J of work on an object moving along a straight horizontal path, accelerating it from an initial speed of 2.0 m/s to a final speed of 6.0 m/s. According to the work–energy theorem, what is the mass of the object?

   • A) 3.0 kg
   • B) 6.0 kg
   • C) 12 kg
   • D) 24 kg
5. 5.

   A constant horizontal pulling force of 25 N moves a 4.0 kg sled across a horizontal surface against a constant resistive friction force of 5.0 N. If the sled starts from rest, what is its kinetic energy after it has traveled a distance of 6.0 m?

   • A) 30 J
   • B) 150 J
   • C) 120 J
   • D) 180 J
6. 6.

   A 1200 kg car traveling at 20 m/s along a horizontal road is brought to rest by a constant net braking force of 6000 N. According to the work–energy theorem, what is the stopping distance of the car?

   • A) 80 m
   • B) 20 m
   • C) 40 m
   • D) 60 m
7. 7.

   A net work of 80 J is done on a 5.0 kg object moving along a straight line, increasing its speed to 6.0 m/s. What was the initial speed of the object?

   • A) 1.0 m/s
   • B) 4.0 m/s
   • C) 2.0 m/s
   • D) 3.0 m/s
8. 8.

   A crate of mass 8.0 kg is pushed from rest across a frictionless horizontal floor by a constant horizontal force. If the crate reaches a speed of 6.0 m/s after moving a distance of 12 m, what is the magnitude of the force applied to the crate?

   • A) 12 N
   • B) 24 N
   • C) 48 N
   • D) 4.0 N
9. 9.

   A 2.0 kg block moves along a horizontal surface with an initial speed of 10 m/s when a constant retarding force of 9.0 N is applied opposite to its direction of motion. According to the work–energy theorem, what is the speed of the block after it has traveled a distance of 4.0 m under the action of this force?

   • A) 4.0 m/s
   • B) 6.0 m/s
   • C) 7.0 m/s
   • D) 8.0 m/s
10. 10.

    A constant net force acts on a 4.0 kg object moving along a straight, frictionless horizontal surface, increasing its speed from 3.0 m/s to 5.0 m/s. What is the net work done on the object?

    • A) 32 J
    • B) 8.0 J
    • C) 50 J
    • D) 64 J