Finding total force - Is this correct?

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To find the total force exerted by the weightlifter, one must consider both the gravitational force acting on the weight and the force applied to accelerate it. The net force calculated as (140 kg)*(0.47 m/s^2) only accounts for the acceleration and neglects the weight of the lifter and the lifted object. The total force includes the gravitational force on both the weightlifter and the weight, plus the force needed for acceleration. Newton's laws, particularly the second and third, are relevant in this context for understanding the forces involved.
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Homework Statement



A weight lifter who has a mass of 90kg lifts a weight of 50kg, which accelerates the weight at a rate of 0.47 m/s^2

Would the total force simply be (140kg)*(0.47m/s^2) = 65.8 n?

Homework Equations





The Attempt at a Solution

 
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nukeman said:

Homework Statement



A weight lifter who has a mass of 90kg lifts a weight of 50kg, which accelerates the weight at a rate of 0.47 m/s^2

Would the total force simply be (140kg)*(0.47m/s^2) = 65.8 n?

Homework Equations





The Attempt at a Solution


That would actually be your net force. You forgot the force of gravity.

Additionally, I don't think the weightlifter is accelerating into the air - only the weight.
 
ahh, net force.

Can you possibly point me in the right direction for total force for my example?
 
Can anyone else help me out with this one?

Thanks :)
 
You have the force of gravity on the weightlifter.

You not only have the force of gravity on the weight, but the weightlifter is applying a force to accelerate it.

This would be the total force applied to the floor the weightlifter is standing on.
 
BobG said:
You have the force of gravity on the weightlifter.

You not only have the force of gravity on the weight, but the weightlifter is applying a force to accelerate it.

This would be the total force applied to the floor the weightlifter is standing on.

Thank you... How would I calculate this?

So, I am asking to identify which laws are being used.

This would be Newtons 3rd correct?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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