Question to help me understand Impulse and momentum?

I sympathise - momentum and impulse are two of the most difficult ideas in Physics, as you can't see or handle either of them. But you're doing well. Yes, Impulse = change of momentum. Yes, impulse = Force * time (in seconds). and yes, the impulse here is = 4 * 2 = 8 Ns. (Note - the unit of impulse is officially "Newton seconds"; the unit of 'change of momentum' is officially "kg m/s". but don't sweat it). So the change in momentum is 8 kg m/s. {I suspect the question setter meant to ask for the change in velocity but made a mistake. Also, there seem to be no units for time - should be "2 seconds". Finally, they broke rule 2 - as set, the data for the mass of the ball is not needed so should not be given. But we all have our off days - be gentle.} In a nutshell, the idea of momentum is just to help us solve collision questions - it has no other use. Similarly, the idea of money is just to solve problems about exchanging things fairly - it has no other use. But at least there are banknotes - momentum is totally an invented concept. But you can learn to deal with it.

You understand. That is exactly what Impulse and momentum is. Change in momentum = impulse. There are 4 variables, given any 3, solve for the unknown. Mass * velocity (change in either or both) = force * time What we are doing is adding TIME to F = MA ====> F * time = M* A *time. All we did was multiply both sides by time. That's legal and it gives us another useful tool (equation) to analyze motion. Newtons * seconds = mass * acceleration * seconds N* s = M *A* t And. V = A*t N*s = M*V So what does this do for us? If we apply 5 N to 10 kg for 5 seconds, what is the velocity change of the object? 10 kg * V = 5 N * 5 s. Solve for V If we are driving a 1000 kg car at 22 m/s and the brakes/tires can generate 800 N of Force, how long to slow down to 10 m/s? 1000 kg * ( 22 - 10)m/s = 800 N * t. Solve for t Etc

You understand. That is exactly what Impulse and momentum is. Change in momentum = impulse. There are 4 variables, given any 3, solve for the unknown. Mass * velocity (change in either or both) = force * time What we are doing is adding TIME to F = MA ====> F * time = M* A *time. All we did was multiply both sides by time. That's legal and it gives us another useful tool (equation) to analyze motion. Newtons * seconds = mass * acceleration * seconds N* s = M *A* t And. V = A*t N*s = M*V So what does this do for us? If we apply 5 N to 10 kg for 5 seconds, what is the velocity change of the object? 10 kg * V = 5 N * 5 s. Solve for V If we are driving a 1000 kg car at 22 m/s and the brakes/tires can generate 800 N of Force, how long to slow down to 10 m/s? 1000 kg * ( 22 - 10)m/s = 800 N * t. Solve for t Etc