Answer:
50
Explanation:
The mechanical advantage of a machine is given by

where
is the output force
is the input force
For the crowbar in this problem,
is the force in input applied by the worker
is the force that the machine must apply in output to overcome the resistance of the window and to open it
Substituting into the equation, we find

Answer:
Explanation:
Given
time of contact between bat and ball is 
suppose u is the incoming velocity and v is the final velocity after collision

Impulse exerted is given by change in momentum of the particle.
Initial momentum 
Final momentum 
Change in momentum 
Impulse 


The work done to pull the sled up to the hill is given by

where
F is the intensity of the force
d is the distance where the force is applied.
In our problem, the work done is

and the distance through which the force is applied is

, so we can calculate the average force by re-arranging the previous equation and by using these data:
The formula for potential energy is
E(p) = mgh
(Mass x gravity x height)
Therefore energy = (5.3)(9.8)(6.6)
= 342.8 J
How did I get 9.8?
9.8 is the constant for gravity
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