Bookworm_321

I am sorry for not mentioning it before it decelerate in the period of 4 seconds to 4ms-2

the question is,( please excuse me if there are any mistakes with grammar or language in particular The weight of an object is 5N. At a certain instant, its momentum is 6kgms-1. Due to a force applied in the direction opposite to the direction of motion. The velocity of the object decreased to 4ms-1. What is the force exerted on the object? so, the way I tried to solve this was by first finding the mass using the weight by taking the acceleration as the gravitation force but I took it by rounding 9.8ms-2 as 10ms-2 .and I got the mass as 0.5kg. Then, I used that mass with the formulae of momentum and found the velocity which was 12ms-1. After that I found the deceleration of the object that was 2ms-2. And to find the force that was exerted on the object to make it decelerate , I multiplied the mass which I found earlier as 0.5kg and the acceleration as 2ms-2 and got the answer as 1N. is anything wrong in the way I tried to solve this question? If so please correct me where I did wrong