C. element only one substance
Answer:
The force is Inertia
Explanation:
The force that acts on an object to move it from rest or a constant straight line motion is known as Inertia.
In physics the above statement is governed by Newton's first law of motion which is also known as Law of Inertia.
This law states that, an object that is at rest will remain at rest and an object that is moving will continue to move in a straight line with constant speed, if and only if the net force acting on the object is zero.
This implies that, A stationary object will remain motionless if no force acts on it while a object with constant velocity will continue moving with constant velocity until a force acts on it (neglecting resistance from air and friction).
Answer:
Both of them reach the lake at the same time.
Explanation:
We have equation of motion s = ut + 0.5at²
Vertical motion of James : -
Initial velocity, u = 0 m/s
Acceleration, a = g
Displacement, s = h
Substituting,
s = ut + 0.5 at²
h = 0 x t + 0.5 x g x t²

Vertical motion of John : -
Initial velocity, u = 0 m/s
Acceleration, a = g
Displacement, s = h
Substituting,
s = ut + 0.5 at²
h = 0 x t + 0.5 x g x t²

So both times are same.
Both of them reach the lake at the same time.
Answer:
Explanation:
1) Force Friction = Normal Force * Coefficient of Friction
Force Friction = Mass * Gravity * Coefficient of Friction
2) F = ma
Force = mass * acceleration
Force Friction (from #1) = mass * acceleration
acceleration = Force Friction / Mass