An object is at rest at time \(t = 0\). The variation with \(t\) of the acceleration \(a\) of the object is shown from \(t = 0\) to \(t = 20{\text{ s}}\).

What is the speed of the object when \(t = 15{\text{ s}}\)?

A.     \({\text{25 m}}\,{{\text{s}}^{ - 1}}\)

B.     \({\text{50 m}}\,{{\text{s}}^{ - 1}}\)

C.     \({\text{75 m}}\,{{\text{s}}^{ - 1}}\)

D.     \({\text{100 m}}\,{{\text{s}}^{ - 1}}\)

B

Think units.

If we want a speed then this can only be calculated from the area under the graph.