Questions: Each sketch below shows three objects with an electric charge. In each case, decide whether there is a net force acting on the object outlined in green. If there is a net force, decide whether it pushes the green-ring object to the left or right. Then select the appropriate button under the sketch. For example, if there is a net force pushing the green-ring object in the first sketch to the left, select the left button under the first sketch. If there is no net force on the green-ring object in the second sketch, select the middle button under the second sketch. And so on.

Each sketch below shows three objects with an electric charge. In each case, decide whether there is a net force acting on the object outlined in green. If there is a net force, decide whether it pushes the green-ring object to the left or right. Then select the appropriate button under the sketch.

For example, if there is a net force pushing the green-ring object in the first sketch to the left, select the left button under the first sketch. If there is no net force on the green-ring object in the second sketch, select the middle button under the second sketch. And so on.

Transcript text: Each sketch below shows three objects with an electric charge. In each case, decide whether there is a net force acting on the object outlined in green. If there is a net force, decide whether it pushes the green-ring object to the left or right. Then select the appropriate button under the sketch. For example, if there is a net force pushing the green-ring object in the first sketch to the left, select the left button under the first sketch. If there is no net force on the green-ring object in the second sketch, select the middle button under the second sketch. And so on.

Solution

Solution Steps

Step 1: Analyze the first diagram

The green-ringed object has a charge of \(+1\). The red object to its left has a charge of \(-1\). Opposite charges attract, so the \(-1\) charge pulls the \(+1\) charge to the left. The blue object to its right has a charge of \(+3\). Like charges repel, so the \(+3\) charge pushes the \(+1\) charge to the left. Both forces act to the left, so the net force is to the left.

Step 2: Analyze the second diagram

The green-ringed object has a charge of \(+1\). The red object to its left has a charge of \(-1\). Opposite charges attract, so the \(-1\) charge pulls the \(+1\) charge to the left. The red object to its right has a charge of \(-2\). Opposite charges attract, so the \(-2\) charge pulls the \(+1\) charge to the right. The force to the right is stronger because the magnitude of the charge is greater (\(|-2| > |-1|\)), so the net force is to the right.

Step 3: Analyze the third diagram

The green-ringed object has a charge of \(+1\). The red object to its left has a charge of \(-3\). Opposite charges attract, so the \(-3\) charge pulls the \(+1\) charge to the left. The red object to its right has a charge of \(-3\). Opposite charges attract, so the \(-3\) charge pulls the \(+1\) charge to the right. The magnitudes of the charges are equal, so the net force is zero.