Machanical

Question

a force of 10n is applied to a vehicle of mass 250kg. This causes the vehicle to increase it's speed from 0.12m/s to 0.6m/s. Calculate:

a)the change in momentum of the vehicle 

b)the value of the acceleration

Answer 1

The change in momentum = ΔP = Δ(mv) but in this case the mass of the vehicle is constant, and only the velocity changes so really, it becomes: change in momentum = mΔV

ΔV means V_final - V_initial

The change in velocity is 0.6 m/s - 0.12 m/s = 0.48 m/s (positive number indicates the vehicle is accelerating)

 

Therefore the change in momentum of the vehicle is: (250kg)*(0.48m/s) = +120 kg*m/s

 

Now for the second part:

 

By Newton's Second Law, Net Force = Mass * Acceleration

 

Since F=ma

 

a = F/m

 

a = (10N) / (250kg) = +0.04 m/s² is the acceleration

 

 

In case you are interested in wondering why we know the unit is m/s², it is because:

 

Newtons / kg = m/s²

 

how?

 

F=ma

1 Newton = (1kg)*(1m/s²)

 

Thus, Newtons / kg is the same thing as saying (kg)*(m/s²) / kg

(kg)*(m/s²) / kg

and you're left with m/s² :)

 

Hope this helped