Hi there!
Recall Newton's Second Law:

∑F = net force (N)
m = mass (kg)
a = acceleration (m/s²)
We must begin by solving for the acceleration using the following:
a = Δv/t
In this instance:
Δv = 3 m/s
t = 2.5 sec
a = 3/2.5 = 1.2 m/s²
Now, plug this value along with the mass into the equation for net force:

Answer:
Force of friction is (-30 N).
Explanation:
The force applied on the box across the floor is 30 N.
The force of gravity is (-8 N) and the the normal force is 8 N.
It is based on Newton's third law of motion. Newton's third law of motion states that the force acting on object 1 to object 2 is equal in magnitude of the force from object 2 to 1 but in opposite direction.
Here there is force of 30 N is applied in horizontal direction. The frictional force act in opposite direction. So, the force of friction is -30 N so that box across the floor.
Answer: its linear momentum is 1.78 × 10²⁹ kg.m/s
Explanation:
Given that;
mass of Earth m = 5.972 x 10²⁴ kg
radius r = 1.496 x 10¹¹ m
period t = 3.15 x 10⁷ s
now we know that Earth rotates in a circular path so the distance travelled per rotation is;
d = 2πr we substitute
d = 2π × 1.496 x 10¹¹ m
= 9.4 × 10¹¹ m
Now formula for speed v is;
v = d/t
we substitute
v = 9.4 × 10¹¹ m / 3.15 x 10⁷ s
v = 2.98 × 10⁴ m/s
now we determine the linear momentum p
linear momentum p = mv
we substitute
p = (5.972 x 10²⁴ kg) × (2.98 × 10⁴ m/s)
p = 1.78 × 10²⁹ kg.m/s
Therefore its linear momentum is 1.78 × 10²⁹ kg.m/s
15 nitrogen atoms are in one molecule
When Living things die,it takes them millions of years to form fossil fuels and as we are using more fossil fuels,the dead and decaying organisms cannot replenish the amount of fossil fuels humans are using as it takes a long time.Hence fossil fuels are not a renewable source of energy.