Solve Momentum Question: 5kg Object, 15 kg m/s, 8 m/s in 15s

[zaga04]

Homework Statement

1. A 5kg object has a momentum of 15 kg m/s. What is the net force required to accelerate the object to 8 m/s over 15 seconds?
A) .35N
B) 1.7N
C) 5.1 N
D) 11 N
E) 23 N

Homework Equations

F=deltaP/deltaT

The Attempt at a Solution

So I use that formula (which I am not sure is right). so wouldn't it be mv/t. So, (5)(8)/15 which is 2.67N which is not an answer choice.

I think I am using the wrong formula, but it's all I can think of! Please help.

 

[kuruman]

The acceleration is not v/t in this case. The object has initial velocity because its momentum is 15 kg m/s before it starts accelerating.