It's still 20 kg. Mass doesn't change according to gravity, only weight changes.
The potential energy of the block is A) 490 J
Explanation:
The potential energy of an object is the energy possessed by the object due to its position in the gravitational field.
It is calculated as follows:

where
m is the mass of the object
g is the acceleration due to gravity
h is the height of the object above the ground
For the block in this problem, we have:
m = 10 kg

h = 5 m
Therefore, its potential energy is:

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Answer:
v_{ average} = 5.57
Explanation:
The most probable value of a measure is
v_average =
∑ x_i
where N is the number of measurements
in tes case N = 3
v_{average} = ⅓ (5.63 +5.54 + 5.53)
V_{average} = 5,567
The number of significant figures must be equal to the number of figures that have the least in the readings.
v_{ average} = 5.57
Explanation:
initial velocity(u) = 90 km/s = 25 m/s
time (t) = 5 sec
mass (m) = 200 kg
final velocity (v) = 0 m/s
v = u + at
0 = 25 + a * 5
-25 = 5 a
-5 = a
Therefore acceleration = -5m/s²
Force = mass * acceleration
F = 200*-5
F = -1000 N