Hello!
To find momentums we need the speeds before and after collision. The simplest way to find these speeds is to use the energy conservation law.
Before falling a ball had only potential energy `mgh_1.` Just before collision it had only kinetic energy `mV_1^2/2, `  and they was equal. Therefore `V_1=sqrt(2gh_1),` where `h_1=3m.`
The same consideration gives that the speed after the collision is `V_2=sqrt(2gh_2)` , where `h_2=2m. ` Now we can answer (1) and (3).
(1) the momentum...
Hello!
To find momentums we need the speeds before and after collision. The simplest way to find these speeds is to use the energy conservation law.
Before falling a ball had only potential energy `mgh_1.` Just before collision it had only kinetic energy `mV_1^2/2, `  and they was equal. Therefore `V_1=sqrt(2gh_1),` where `h_1=3m.`
The same consideration gives that the speed after the collision is `V_2=sqrt(2gh_2)` , where `h_2=2m. ` Now we can answer (1) and (3).
(1) the momentum before collision is `mV_1 approx 0.61((kg*m)/s)` and after is `mV_2 approx 0.50((kg*m)/s).`
(3) note that impulse is a vector, it has the same direction as velocity. The momentum before collision is directed downwards and after -- upwards. So the difference of moments is the sum of their magnitudes, i.e. `1.11 kg*m/s.`
For (2) we have to know that a force may be expressed as the derivative of a momentum (Newton's Second law, actually). Therefore the integral of a force is the difference of momentums. And the average force is this difference divided by a time. Force is upwards all the time.
(2) average force is `(1.11)/(5*10^(-3)) approx 222(N).`
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