Urgent, urgent!! Quick answers. A junior high school junior high school, about the topic of mechanic

1) (v metal gold) g = (v metal water) g + f

2) (v metal gold) g + g0 = (v metal water) g + f

Landlord, ask for Figure A and Figure B.

W has = g car * h w total work = f * s length = g car *

w has w total work =

Solve the equation to get s=40000m

The meaning of the title is: When a car drives from the ground to the top of a mountain, it is equivalent to converting the work done into gravitational potential energy, which is the legendary useful work. However, if you drive up, you have to have friction to consume energy, and you can't go up vertically.

So, the title tells you that if you remove those that are consumed, the useful work will only account for 60% of the total work.

Total work = power * work distance, the power here defaults to its reaction force - friction Friction tells you again, which is equal to times the weight of the car.

Now that I've told you everything, let's go for the questions

Multiply the calculated result by the mechanical efficiency.

I think there is a condition missing: when pulling a or b, it will rise at a constant speed. This topic includes the fact that the mass of the bottom wheel in the pulley block cannot be ignored.

The tensile force is 3F and 5F respectively, G1: G2=2:1, and let the weight of the bottom wheel be G, then there are: 3F=G1+G and 5F=G2+G to obtain G=G1 2 If the rope is under the action of force F, the object A rises H, then the bottom wheel rises to H

The useful work w1=g1xh total work is w=g1xh+gxh, and all mechanical efficiency is 2 3

I didn't check it carefully, and if it was wrong, please correct it.

The exercise must be marked as a constant ascension.

w has w total = gh fnh = g fn = mg fn known object mass ratio is 1:2, tensile force f ratio is 3:5, so the ratio of mechanical efficiency in the two cases of pulley block is.

1:2) (3:5) = 5:6, if we know the mechanical efficiency when we lift B, we know the mechanical efficiency when we lift A.

I ignore that of course it is 100%, if there is no work loss, efficiency = useful work Total work, 2 equal, it is 100%.

Useful work: w has=gh=

W total = g person xh + fs =

Efficiency = 200 600 =.

The required preload fn=f*c f=1250*

Bolt tensile stress fa=(fn 2) a=(fn 2) ( *d1*d1 4)=(substitute value)=

Therefore, the strength is sufficient.