Final answer:
The magnitude of the resultant force can be calculated using the law of cosines. Apply the formula R = √(F1² + F2² + 2 · F1 · F2 · cos(θ)) with the given forces and angle, and round the result to the nearest hundredth of a newton to find the correct choice.
Step-by-step explanation:
To find the magnitude of the resultant force when two forces act on a body at an angle, you can use the formula that comes from the law of cosines:
R = √(F1² + F2² + 2 · F1 · F2 · cos(θ))
Where R is the resultant force, F1 and F2 are the magnitudes of the two forces, and θ is the angle between them. For the forces of 25 newtons and 85 newtons forming a 55° angle:
R = √(25² + 85² + 2 · 25 · 85 · cos(55°))
Calculate the value to get the magnitude of the resultant force. Round the answer to the nearest hundredth to find the correct option from the given choices.