Explanation:
Given that,
Mass of the shopping cart, 
Initial speed of the shopping cart, 
Mass of the box, 
Initial speed of the box,
(at rest)
They stick together and continue moving at a new velocity. It is a case of inelastic collision.
(a) The momentum of the shopping cart before the collision is given by :

(b) The momentum of the box before the collision is given by :

(c) The velocity of the combined shopping cart/box wreckage after the collision is given by using the conservation of momentum as :

Hence, this is the required solution.
The first one? If not I just guessed
Number 20 is B and 21 is C
Explanation:
Fluid gauge pressure is:
P = ρgh
where ρ is the fluid density and h is the depth of the fluid.
P = (1000 kg/m³) (9.8 m/s²) (1642 m)
P = 16,091,600 Pa
Rounded to four significant figures, the gauge pressure is 16.09 MPa.
Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere "behaves" over relatively long periods of time.