Answer:
(a) 2400N
(b) Yes
Explanation:
(a) Mass (m) = 1.5kg, initial speed (v) = 4m/s, time (t) = 2.5milliseconds = 2.5/1000 = 0.0025seconds
F = mv/t = (1.5×4)/0.0025 = 6/0.0025 = 2400N
(b) The force would be different because the mass of the two hands and forearms is 3kg (2 × 1.5kg = 3kg)
Answer:
The fluids speed at a)
and b)
are
and
respectively
c) Th volume of water the pipe discharges is:
Explanation:
To solve a) and b) we should use flow continuity for ideal fluids:
(1)
With Q the flux of water, but Q is
using this on (1) we have:
(2)
With A the cross sectional areas and v the velocities of the fluid.
a) Here, we use that point 2 has a cross-sectional area equal to
, so now we can solve (2) for
:

b) Here we use point 2 as
:

c) Here we need to know that in this case the flow is the volume of water that passes a cross-sectional area per unit time, this is
, so we can write:
, solving for V:

Point of reference - an indicator that orients you generally; "it is used as a reference for comparing the heating and the electrical energy involved"
The box is kept in motion at constant velocity by a force of F=99 N. Constant velocity means there is no acceleration, so the resultant of the forces acting on the box is zero. Apart from the force F pushing the box, there is only another force acting on it in the horizontal direction: the frictional force

which acts in the opposite direction of the motion, so in the opposite direction of F.
Therefore, since the resultant of the two forces must be zero,

so

The frictional force can be rewritten as

where

,

. Re-arranging, we can solve this equation to find

, the coefficient of dynamic friction:
The answer is the Milky Way .