What does magnitude of displacement mean?

Question

As in: A car is capable of accelerating at a uniform rate of .85m/s2. What is the magnitude of the car's displacement as it accelerates uniformly from a speed of 83km/h to one of 94 km/h?

Please correct wrong steps in my chain of thought: I started by changing .85m/s2 to km/h by multiplying the entire thing by 1000/3600. Then I got stuck as I didn't know what magnitude of displacement was. Is it a measurement in m/s. Or seconds? Or metres?

To sdstrat: Sounds like you know what you're talking about, but I don't. Please explain better if you're reading.

Answer 1

Displacement is a vector having both magnitude |S| and direction (e.g., north, south, east, or west). So your question is interested only in |S| and not the direction of the displacement.

Use the SUVAT equation, V^2 = U^2 + (1/2) aS; so that S = 2[V^2 - U^2]/a where a = .85 m/sec^2, V = 94 kph, and U = 83 kph. Change the kph to mps (m/sec) and solve for S in meters. As everything in the SUVAT equation is a scalar, your answer S is also a scalar, which is also called a magnitude.