The force applied to lift the crate is 171 N
Explanation:
The lever works on the principle of equilibrium of moments, so we can write:

where
is the force in input
is the arm of the input force
is the output force
is the arm of the output force
For the lever in this problem, we have:


(force applied)
Solving the equation for
, we find the force applied to lift the crate:

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Answer:
4.15 m/s
Explanation:
Its given that acceleration is 0.1 m/s² with a direction opposite to the velocity. Since, the direction of acceleration is opposite to the velocity, this gives us a hint that the velocity is decreasing and so acceleration would be negative.
i.e.
acceleration = a = - 0.1 m/s²
Distance covered = S = 6m
Velocity after covering 6 meters = Final velocity =
= 4 m/s
We need to find the initial speed, which will be the same as the magnitude of initial velocity.
Initial velocity =
= ?
3rd equation of motion relates the acceleration, distance, final velocity and initial velocity as:

Using the known values in the formula, we get:

Thus, the initial speed of the ball was 4.15 m/s
The net force on the student is A) -294 N
Explanation:
Neglecting air resistance, there is only one force acting on the student: the force of gravity, which is given by

where
m is the mass of the student
g is the acceleration of gravity
In this problem, we have:
m = 30 kg is the mass of the student
is the acceleration of gravity, where the negative sign means the direction is downward
Substituting, we find the force of gravity on the student:

And since this is the only force acting on the student, it is also the net force on him.
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Answer:
The mass of the products and reactants are the same on both sides of the equation.
The number of atoms of products and reactants are equal and hence it proves the law of conservation of mass.
.
Answer:
Energy conservation.
Explanation:
The 1st Law of Thermodynamics is a statement about energy conservation. It states that
, which means that if we <u>substract the work W done</u> by the system to the <u>heat Q given</u> to the system we get the <u>change in the internal energy</u>
, so any excess in energy given to the system appears as internal energy, stating that energy is conserved.