Work (College Board AP® Physics 1: Algebra-Based): Exam Questions

Define the term conservative force and give one example of a conservative force.

In a physics lesson on work, Student A makes the following claim:

"The work done by a conservative force is path-independent."

Indicate whether Student A is correct or incorrect.

Justify your reasoning.

A roller coaster cart starts at the passenger entrance and exit point. The cart climbs a track inclined at $50°$ to the horizontal, rising through a vertical height of $100\text{m}$. It then completes three vertical loops of decreasing height and finally travels horizontally back to the passenger entrance and exit point, where it stops.

Indicate whether the gravitational potential energy $U_g$ of the cart–Earth system when the cart is in its final position is greater than, less than, or equal to the gravitational potential energy $U_{g0}$ of the system when the cart is in its initial position by writing one of the following:

• $U_g<U_{g0}$

• $U_g=U_{g0}$

• $U_g>U_{g0}$

Use ideas about work to justify your reasoning.

Give one example of a nonconservative force.

An unknown force acts on an object. The total mechanical energy of the object-Earth system before the force acted is greater than the total mechanical energy after the force acted.

Indicate whether the unknown force is conservative or nonconservative.

⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽ conservative‎ ‎ ‎‎ ‎ ‎ ‎ ‎ ‎ ‎ ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽ nonconservative

Justify your reasoning.

A skier skis down a slope in a zig-zag pattern from left to right as they descend the mountain side.

Use the idea that the work done by a nonconservative force is path dependent to explain why the skier descends the mountain side in this way.

State the two conditions that must apply for the following equation to be used to calculate the work done by a force on an object:

$W=Fd$

A constant force is applied to an object on a flat, frictionless horizontal surface. As the object moves along the surface, the force is directed at an angle of $70°$ to the object's displacement.

Indicate whether the object's final kinetic energy $K$ is greater than, less than, or equal to its initial kinetic energy $K_0$ by writing one of the following:

• $K>K_0$

• $K=K_0$

• $K<K_0$

Justify your reasoning.

The object is now at rest on the same frictionless horizontal surface. A different constant force is applied to the object, directed vertically downward, perpendicular to the surface.

Predict how the motion of the object will change. Justify your reasoning.

Describe a procedure that can be used to determine the work done when a nonconstant force displaces an object.