The electrical force acting on a charge q immersed in an electric field is equal to

where
q is the charge
E is the strength of the electric field
In our problem, the charge is q=2 C, and the force experienced by it is
F=60 N
so we can re-arrange the previous formula to find the intensity of the electric field at the point where the charge is located:
Let the key is free falling, therefore from equation of motion
.
Take initial velocity, u=0, so
.

As velocity moves with constant velocity of 3.5 m/s, therefore we can use formula

From above substituting t,
.
Now substituting all the given values and g = 9.8 m/s^2, we get
.
Thus, the distance the boat was from the point of impact when the key was released is 10.60 m.
Answer:
The mass of the mud is 3040000 kg.
Explanation:
Given that,
length = 2.5 km
Width = 0.80 km
Height = 2.0 m
Length of valley = 0.40 km
Width of valley = 0.40 km
Density = 1900 Kg/m³
Area = 4.0 m²
We need to calculate the mass of the mud
Using formula of density


Where, V = volume of mud
= density of mud
Put the value into the formula


Hence, The mass of the mud is 3040000 kg.