Energy of motion (kinetic energy) Knowledge-Based Practice

Questions

1. 1.

   Two blocks with masses $m$ and $3m$ are initially at rest on a frictionless horizontal surface. If identical constant net horizontal forces act on each block over the same displacement, what is the ratio of the final kinetic energy of the lighter block to that of the heavier block?

   • A) 1
   • B) 3
   • C) 1/3
   • D) 9
2. 2.

   If the speed of a moving object is reduced by 50%, by what percentage does its kinetic energy decrease?

   • A) 25%
   • B) 75%
   • C) 50%
   • D) 100%
3. 3.

   An object with an initial kinetic energy of $K$ is accelerated so that its speed triples. What is the net work done on the object in terms of $K$?

   • A) $2K$
   • B) $3K$
   • C) $8K$
   • D) $9K$
4. 4.

   Three identical balls are launched from the top of a tower with the same initial speed in different directions: Ball X horizontally, Ball Y at an angle of 45° above the horizontal, and Ball Z vertically downward. How do the kinetic energies of the three balls compare immediately after release?

   • A) All three balls have the same kinetic energy.
   • B) Ball Z has greater kinetic energy than Ball X and Ball Y.
   • C) Ball X has greater kinetic energy than Ball Y and Ball Z.
   • D) Ball Y has greater kinetic energy than Ball X and Ball Z.
5. 5.

   Car A has a mass of 1200 kg and moves due north at a speed of 10 m/s, while Car B has a mass of 800 kg and moves due south at a speed of 15 m/s. What is the total kinetic energy of the two-car system?

   • A) 150 kJ
   • B) 30 kJ
   • C) 90 kJ
   • D) 0 kJ
6. 6.

   An object of mass $m$ moving at a speed $v$ has kinetic energy $K$. If its kinetic energy increases to $9K$ while its mass remains constant, what is its new speed in terms of $v$?

   • A) $81v$
   • B) $9v$
   • C) $4.5v$
   • D) $3v$
7. 7.

   Two objects, X and Y, have equal kinetic energy. If the mass of object X is four times the mass of object Y, what is the ratio of the speed of object X to the speed of object Y?

   • A) 4
   • B) 2
   • C) 1/4
   • D) 1/2
8. 8.

   A 6.0 kg block slides along a frictionless horizontal surface with a kinetic energy of 48 J. What is the speed of the block?

   • A) 2.0 m/s
   • B) 8.0 m/s
   • C) 16 m/s
   • D) 4.0 m/s
9. 9.

   A 0.5 kg cart moves along a straight track. If its speed increases from 2 m/s to 6 m/s, by how much does its kinetic energy increase?

   • A) 4 J
   • B) 16 J
   • C) 9 J
   • D) 8 J
10. 10.

    A vehicle of mass $m$ travels at a speed $v$ and has a kinetic energy of $E$. If the mass of the vehicle is doubled while its speed is tripled, what is its new kinetic energy?

    • A) $6E$
    • B) $12E$
    • C) $36E$
    • D) $18E$

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