Barron's 2nd Edition DT Q25

Barron's Book

25) This problem asks us to find the acceleration of the object at t=5 seconds. The problem presents us with a lot of unnecessary information to throw us off. All we need to take from this is that at t=5 seconds, there will be a 10 N force in the x-direction and a 10 N force in the negative x-direction. We can draw a simple force diagram for this.

Where F is applied force

Next, we can write an equation of the sum of the forces in the x-direction.

Where m is mass, F is applied force, and a is acceleration

Finally, we can plug in our values and solve for the acceleration.

Where m is mass, and a is acceleration

Answer: A