An object is thrown vertically upward with a nonzero velocity. If gravity is turned off at the instant the object reaches the maximum height, what happens?

Options

A. the object continues to move in a straight line
B. the object will be at rest
C. the object falls back with uniform velocity
D. the object falls freely

Answer

To solve the problem, we need to analyze the motion of the object when it is thrown vertically upward and what happens when gravity is turned off at the maximum height.

### Step-by-Step Solution:

1. **Understanding the Initial Conditions**:
- An object is thrown vertically upward with a non-zero initial velocity. As it moves upward, it experiences a downward acceleration due to gravity (denoted as \( g \)).
- At the maximum height, the vertical component of the velocity becomes zero (\( v_y = 0 \)), but the object may still have a horizontal component of velocity if it was thrown at an angle.

2. **Maximum Height**:
- At the maximum height, the object momentarily stops moving upward. The forces acting on it are due to gravity, which is pulling it downward.
- If gravity is still acting, the object would start to fall back down after reaching the maximum height.

3. **Turning Off Gravity**:
- The question states that gravity is turned off at the instant the object reaches the maximum height.
- When gravity is turned off, there is no longer any force acting on the object. This means that the object will not experience any acceleration.

4. **Motion After Gravity is Turned Off**:
- Since there is no gravitational force acting on the object, it will not accelerate downward.
- The object will maintain its state of motion according to Newton's First Law of Motion, which states that an object in motion will remain in motion at a constant velocity unless acted upon by a net external force.

5. **Conclusion**:
- At the maximum height, with gravity turned off, the object will remain stationary at that height because there is no force to pull it down or push it in any other direction.
- Therefore, the correct conclusion is that the object will be at rest at the maximum height.

### Final Answer:
The object will remain stationary at the maximum height when gravity is turned off.