To solve this problem, we need to analyze the change in direction of the football player.$\\$Initially, the player is moving southward. When the player turns eastward,$\\$the direction of velocity changes, but the speed remains constant.$\\$The change in velocity is a vector quantity, and it can be calculated as follows:$\\$• Initial velocity vector $\vec{v}_i$ is directed southward.$\\$• Final velocity vector $\vec{v}_f$ is directed eastward.$\\$The change in velocity $\Delta \vec{v}$ is given by:$\\ \Delta \vec{v} = \vec{v}_f - \vec{v}_i \\$Since $\vec{v}_i$ is southward and $\vec{v}_f$ is eastward, we can represent them as:$\\ \vec{v}_i = -v \hat{j} \quad$(southward)$\\ \vec{v}_f = v \hat{i} \quad$(eastward)$\\$Thus, the change in velocity is:$\\ \Delta \vec{v} = v \hat{i} - (-v \hat{j}) \\ \Delta \vec{v} = v \hat{i} + v \hat{j} \\$This change in velocity vector $\Delta \vec{v}$ is directed towards the north-east.$\\$The force acting on the player is responsible for this change in velocity,$\\$and it acts in the same direction as $\Delta \vec{v}. \\$Therefore, the force that acts on the player while turning is along north-east.$\\$This corresponds to Option 3.