A 2.0-kg object has a velocity of 4.0 î m/s at t = 0.A constant resultant force of (2.0 î0 + 4.0 ĵ )N then acts on the object for 3.0 s.What is the magnitude of the object's velocity at the end of the 3.0-s interval?
A)9.2 m/s
B)6.3 m/s
C)8.2 m/s
D)7.2 m/s
E)7.7 m/s

Question

Quizplus · Accepted Answer

The initial velocity is 4.0 î m/s. The acceleration is force/mass = (2.0 î + 4.0 ĵ) N / 2.0 kg = (1.0 î + 2.0 ĵ) m/s². After 3 seconds, the change in velocity is (3.0 s) * (1.0 î + 2.0 ĵ) m/s² = (3.0 î + 6.0 ĵ) m/s. The final velocity is (4.0 î + 0 ĵ) + (3.0 î + 6.0 ĵ) = (7.0 î + 6.0 ĵ) m/s. The magnitude is √(7.0² + 6.0²) = √(49 + 36) = √85 ≈ 9.2 m/s.

A 20-Kg Object Has a Velocity of 4