What will the sailboat do based on the arrows' lengths and directions?

• A. It will move backward
• B. It will stop
• C. It will speed up only
• D. It will speed up and then move at a constant speed

Answer: (D)

Net force determines how motion changes. The sailboat is pushed forward by wind, so there’s a forward force. At first this forward push is stronger than the resisting forces from drag and water, giving a net forward force and causing the boat to accelerate—that’s the “speed up” part. As the boat speeds up, drag increases, shrinking the net forward force. When drag grows to balance the wind’s push, the net force becomes zero, so there’s no more acceleration and the boat settles into a steady, constant speed. That sequence—speeding up first, then moving at a constant speed—matches the described scenario.