Work–energy theorem Knowledge-Based Practice

Questions

1. 1.

   A crate is pushed across a horizontal floor at a constant speed of 2.0 m/s over a distance of 5.0 m by a constant horizontal force of 30 N. According to the work–energy theorem, what is the net work done on the crate?

   • A) 0 J
   • B) 150 J
   • C) -150 J
   • D) 60 J
2. 2.

   A constant force of 25 N directed at an angle of $60^\circ$ above the horizontal pulls an object along a frictionless, level floor through a displacement of 8.0 m. According to the work–energy theorem, what is the change in the kinetic energy of the object?

   • A) 0 J
   • B) 173 J
   • C) 200 J
   • D) 100 J
3. 3.

   A constant braking force brings a crate traveling at speed $v$ to rest over a stopping distance $d$ along a horizontal floor. According to the work–energy theorem, what stopping distance is required to bring the same crate to rest from an initial speed of $2v$ using the same braking force?

   • A) $d$
   • B) $\sqrt{2}d$
   • C) $2d$
   • D) $4d$
4. 4.

   An object moves along a straight line on a horizontal surface while a constant horizontal applied force acts in the direction of motion. Over a displacement of 5.0 m, the kinetic energy of the object increases from 25 J to 85 J against a constant friction force of 6.0 N. What is the magnitude of the applied force?

   • A) 18 N
   • B) 12 N
   • C) 23 N
   • D) 6.0 N
5. 5.

   Two carts, cart X of mass $m$ and cart Y of mass $2m$, are initially at rest on a frictionless horizontal surface. If the same constant net horizontal force is exerted on each cart over the same displacement, what is the ratio of the final kinetic energy of cart X to that of cart Y?

   • A) 1 : 4
   • B) 1 : 2
   • C) 1 : 1
   • D) 2 : 1
6. 6.

   A net work of $-96\text{ J}$ is done on an object moving along a straight horizontal path, causing its speed to decrease from $10.0\text{ m/s}$ to $6.0\text{ m/s}$. According to the work–energy theorem, what is the mass of the object?

   • A) 3.0 kg
   • B) 1.5 kg
   • C) 6.0 kg
   • D) 12.0 kg
7. 7.

   A net work of $W$ accelerates an object from rest to a speed of $v$. According to the work–energy theorem, what additional net work must be done on the object to increase its speed from $v$ to $3v$?

   • A) $3W$
   • B) $8W$
   • C) $9W$
   • D) $2W$
8. 8.

   A 2.0 kg block moves along a straight, frictionless horizontal surface, accelerating from an initial speed of 4.0 m/s to a final speed of 10.0 m/s. According to the work–energy theorem, what is the net work done on the block?

   • A) 36 J
   • B) 100 J
   • C) 168 J
   • D) 84 J
9. 9.

   A 1500 kg vehicle traveling at 20 m/s along a straight, level road is brought to rest over a distance of 40 m. According to the work–energy theorem, what is the magnitude of the average net force acting on the vehicle?

   • A) 3750 N
   • B) 5000 N
   • C) 7500 N
   • D) 15,000 N
10. 10.

    A net work of 32 J is done on a 4.0 kg object that is initially moving at 3.0 m/s along a frictionless horizontal track. What is the final speed of the object?

    • A) 4.0 m/s
    • B) 5.0 m/s
    • C) 7.0 m/s
    • D) 8.0 m/s

Answers and step-by-step solutions appear after you finish the test.