A 5 kg block is moving at 2 m/s along the x-axis. A constant 3 N force acts for 3 s. What is the final velocity if no other forces act?

A 5 kg block is moving at 2 m/s along the x-axis. A constant 3 N force acts for 3 s. What is the final velocity if no other forces act?

• A. 2.6 m/s
• B. 4.0 m/s
• C. 5.0 m/s
• D. 3.8 m/s

Answer: (D)

When a constant force acts on a mass, it produces a constant acceleration given by a = F/m. Here the acceleration is a = 3 N / 5 kg = 0.6 m/s^2 in the positive x direction. Over 3 seconds, the velocity changes by Δv = a t = 0.6 × 3 = 1.8 m/s. Starting from 2 m/s, the final velocity becomes 2 + 1.8 = 3.8 m/s along the x-axis. This result matches both the force applied and the time interval. For comparison, getting 2.6 m/s would need only 1 s at this acceleration, 4.0 m/s would require about 3.33 s, and 5.0 m/s would require 5 s, none of which fit the given 3 s.

When a constant force acts on a mass, it produces a constant acceleration given by a = F/m. Here the acceleration is a = 3 N / 5 kg = 0.6 m/s^2 in the positive x direction. Over 3 seconds, the velocity changes by Δv = a t = 0.6 × 3 = 1.8 m/s. Starting from 2 m/s, the final velocity becomes 2 + 1.8 = 3.8 m/s along the x-axis. This result matches both the force applied and the time interval. For comparison, getting 2.6 m/s would need only 1 s at this acceleration, 4.0 m/s would require about 3.33 s, and 5.0 m/s would require 5 s, none of which fit the given 3 s.