### All AP Physics 1 Resources

## Example Questions

### Example Question #21 : Tension

A 20 kg box hangs in an elevator by a cord rated to withstand a tension force of 250 N. If the elevator, from rest, moves upward until the cord breaks, what was the acceleration of the elevator when the cord broke? Assume .

**Possible Answers:**

None of these

**Correct answer:**

Start with the formula for force and solve for acceleration. Then subtract the acceleration of gravity because the elevator is moving up.

### Example Question #211 : Specific Forces

A spring is attached to a rope that is hanging from the ceiling. A block of mass is attached to the end of the spring which has a constant of . What amplitude would result in a minimum rope tension of ?

Ignore the mass of the rope and spring and assume simple harmonic motion.

**Possible Answers:**

**Correct answer:**

There are two forces contributing to tension in the rope: the weight of the mass and the force of the spring. When the tension of the rope is zero, we know that these two forces are equal and opposite. Furthermore, the weight of the mass will always be pointed down, so the force of the spring (relative to the rope) will be pointed upward. This occurs in a moment of compression of the spring. With that said, we just need to solve the following expression:

Rearranging for displacement:

Plugging in our values:

### Example Question #23 : Tension

Jennifer has a mass of and is swinging on a long rope at . Determine the tension in the rope at the bottom of her swing.

**Possible Answers:**

**Correct answer:**

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