What comes first: Work or kinetic energy? Suppose we have a body initially at rest. Now a force ($F$) is continuously applied on it and it gets displaced by some distance $x$.
My tutor said that from work energy theorem it gains kinetic energy equals to $Fx$ and this work is the cause of gain in kinetic energy.
But I have some confusion:
If this work comes earlier to kinetic energy and is the cause of gain in kinetic energy then why did the body moved in the first place if no motion is possible if velocity of a body is zero?
Let me clarify:
Earlier the body was at rest. When force was applied, it gains some velocity and thus gains kinetic energy and after gaining velocity, the body moves or displaces.
So doesn't that mean that the body gained kinetic energy first and then work was done?
More importantly, which of the two (work and kinetic energy gain) occurs first?
 A: I think that the discussion related to some answers and the original question revolves around the proper definition of causality in physical theories (I won't touch here the philosophical issues connected to this concept).
In physics, we say that a time-dependent quantity $A(t)$ has a causal relation with another time-dependent quantity $B(t)$, if we have a theory connecting $A(t)$ to $B(t')$ for all the times $t>t'$. In such a case, we say that $A$ depends causally on $B$.
The temporal sequence between cause and effect has a central role. This implies that a relation at equal times, $A(t)=B(t)$ can never be seen as causal.
Before getting the work-energy theorem, let me discuss some other examples of causal and not-causal relations in classical mechanics as a preliminary exercise.
The Second Law of Newton's dynamics is not a causal relationship between force ($F(t)$) and the acceleration $a(t)$ of a body subject to that force. It is just a formula connecting these two different quantities at the same time. The same holds (notwithstanding some widespread misconception) for all the action-reaction pairs of forces of the Third Newton's law. Again the fact that force $F_{12}(t)$ of the body $2$ on body $1$ is always equal and opposite to the force $F_{21}(t)$ of the body $1$ on body $2$, at the same time, does not imply a causal relation. In Newtonian dynamics, it is a property of the system of two bodies valid at each time $t$ in a completely symmetric way.
The Second Law of Newton's dynamics  implies a causal relation between the velocity (or position) at time $t$ and the acceleration (then the force) at a previous time $t'<t$. This is formally evident by writing the solution of the differential equation for the velocity $v(t)$ as
$$
v(t)= v(t') + \int_{t'}^t a(\tau) {\mathrm d} \tau.
$$
I find it even clearer a discretized version of the previous equation:
$$
v(t+\Delta t) = v(t) + a(t) \Delta t + O(\Delta t^2).
$$
Now the discussion of the work-energy theorem in terms of causality should be simple.
The theorem states that the work done from time $t_0$ to time $t$ by the resulting force ${\bf F}$ along the trajectory followed by a particle of mass $m$, moving under the action of that force, is equal, at each time t, to the difference of kinetic energy at time $t$ and time $t_0$:
$$
W_{t_0}(t)=\int_{t_0}^t {\bf F}(\tau)\cdot {\bf v}(\tau) {\mathrm d}\tau=\int_{t_0}^t m \frac{d{\bf v}(\tau)}{dt}\cdot {\bf v}(\tau) {\mathrm d}\tau=\frac12 m \left( v^2(t)- v^2(t_0)\right)=\Delta K_{t_0}(t).
$$
It is clear that, for any choice of the initial time, we have the equality of two functions of the time at the same time. Therefore, based on the previous discussion, we do not have a causal connection between $K_{t_0}(t)$ and $W_{t_0}(t)$.
A: One should remember how we define energy in physics, energy is defined as “ the capacity of an object to do work,” basically,the amount of  work  done on an object is equal to the gain/loss in the kinetic energy of the object.Say,as an example;I push an  object,Now; how much work I did would be equal to the energy(in this case,kinetic energy) of the object.For further reading,I recommend reading  about the work-energy theorem to which I am going to link a Wikipedia article below.
Work-Energy Theorem(WikiArticle ): https://en.m.wikipedia.org/wiki/Work_(physics)
A: Work done is energy transferred.
So the energy transferred to the body when it is accelerated is the work done.
Therefore the the work done and the kinetic energy increase at the same time.
A: Work is a transfer of energy by any means that does not depend on a temperature difference.
Therefore, when work occurs energy is transferred. There can be no first or second in this. They are always and must always be at the same time.
It is possible for work to immediately cause a change in potential energy instead of a change of kinetic energy. But whatever the form of the transferred energy, the change in energy occurs simultaneously with the work.
If that were not the case then energy would not be conserved.
A: 
Earlier the body was at rest. When force was applied, it gains some
velocity and thus gains kinetic energy and after gaining velocity, the
body moves.
So doesn't that mean that the body gained kinetic energy first and
then work was done ?

As soon as the body moves it has kinetic energy. The kinetic energy of the body is
$\frac{mv^2}{2}$ where $v$ is the instantaneous velocity. As the velocity increases so does the kinetic energy possessed by the body.
But the body will not attain a velocity from rest unless energy is transferred to the body from something else to accelerate it. That something else is a net force acting through a distance per Newton's second law.
So work comes first.
CLARIFICATION:
My answer is with respect to real bodies, not ideal rigid bodies which do not exist at the macroscopic level. Real bodies don't acquire velocity (and thus kinetic energy) instantaneously (in zero time).
Hope this helps.
A: You have some good correct answers, but you seem to be concerned about the timing. Action and  reaction of forces occur simultaneously. Changes in gravitational or electromagnetic forces can affect the object at the speed of light, contact forces will transmit through the object at its speed of sound, but as soon as each atom is accelerated its KE changes.
A: You've expressed an interesting dilemma: Work involves the application of a force through a distance. Also, considering the example of a block on a frictionless table, work done equals the change in its kinetic energy. So I think you're saying that work can't be done until the block moves through some distance but the block won't move until work is done on it.
But when the force is first applied, by Newton's second law there is an acceleration, i.e., a change in velocity, and the force and acceleration occur simultaneously. The force is what causes the block to start moving and we can calculate its subsequent motion and kinetic energy using Newton's law if we know the force.
Let's say the block moves from x=0 to x=$x_f$. The work/energy relationship is a way of calculating the kinetic energy and therefore the velocity of the block at x=$x_f$ without having to be concerned with the motion of the block at every point along the way. So to return to your dilemma, I think it arises by thinking it is the work done on the block that is causing it to move. Rather it is the force that is doing that.
