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3 years ago

What is the force that can cause two pieces of iron to attract each other?

2 answers:

8 0

Is it A ? Yes ! Two pieces of iron DO always attract each other with equal and opposite gravitational forces, although the forces are so small that we never notice them.

Is it B ? Yes, it could be. If at least one of the pieces of iron is magnetized, then they can attract each other with equal and opposite magnetic forces.

Is it C ? Yes, it could be. But the pieces of iron would have to be joined by a stretched rubber band. Then they would attract each other with equal and opposite elastic forces.

Is it D ? Yes, it could be. If one of the pieces of iron carries a net electric charge, then they attract each other with equal and opposite electrostatic forces.

Rudiy273 years ago

6 0

Answer:

B. Magnetic Force

Explanation:

two pieces of irons cannot attract each other unless at least one of them is magnetize. That force is called magnetism.

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3 years ago

A 250 kg flatcar 25 m long is moving with a speed of 3.0 m/s along horizontal frictionless rails. A 61 kg worker starts walking

Anna11 [10]

Answer:

x=31.09m

Explanation:

p1=p2

The momentum of flatcar and the momentum of the worker so

The velocity of the worker is:

$m_{f}*v_{f}=m_{w}*v_{w}\\\\v_{f}=\frac{m_{f}*v_{f}}{m_{w}}\\v_{f}=\frac{61kg*3.0\frac{m}{s}}{250kg}\\v_{f}=0.732\frac{m}{s}$

The total motion has a total velocity and is

$Vt=v_{w}+v_{f}\\Vt=0.732\frac{m}{s}+3.0\frac{m}{s}\\Vt=3.732\frac{m}{s}$

The time the worker take walking is

$t=\frac{x}{v_{w}}\\t=\frac{25m}{3\frac{m}{s}}=8.33s$

Now the total time and the total velocity determinate the motion of tha flatcar how far has moved

$x=t*Vt\\x=8.33s*3.732\frac{m}{s} \\x=31.09m$

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3 years ago

Jack has two boxes: one is 148g and one is 78g. if jack pushes both boxes with the same amount of force which will accelerate fa

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1) A The 78g
2) C Push on the wagon in the opposite direction as Jack with a force that is the same as Jack is applying.

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3 years ago

14. A block rests on a frictionless table on Earth. After a 20-N horizontal force is applied to the block, it accelerates at 3.9

joja [24]

<span>14. Let's find mass. We know that F = m*a, so m = F/a.m = 20/3,9 m/s^2 = 5,12 kg;We already know the mass, so acceleration will be a = F/m;a = 10/5,12 = 2,0 m/s^2 (approximately);Answer: E.
15. According to the picture given above, let's define all components:These are refer to y: $985N sin(31)= 507;788N cos(32)= 668;411N sin(53)=-328;$
And these are refer to x: $985N cos(31)= 844 788N sin(32)= -417 411N cos(53)= -247$
And finally let's calculate tan: $tan^-1 (507/844)= 30,98; tan^-1 (668/-417)= -58,02; tan^-1 (-328/-247)= 53,01$
According to these calculations we've got: Sum Fx = 179,4 and Sum Fy = 847. Then let's count magnitude: $Fsum = rad 179^2 + 847^2 = 865$
Then we've got [tex]cos^-1 (179/865) = 77.7 (approximately).
So the most approximate answer is C. 866 N at 78.1° counterclockwise to the x-axis.
16. I think that this question is incomplete because there wasn't mentioned in what end of the chain the tension should be calculated. Anyway I'll help you with both bottom and top ends. We will use the basic formula W=m*g; W(bottom) = 175*9.8 = 1715 N; W(top) = (175+12)*9.8 = 1833 N; So you should choose between B. 1830 N or D. 1720 N. But I think the most possible answer is B.
17. I am definitely sure that A diagram generates the most tension in one chain. So the answer is C. The box is held by 1 chain and have all its weight.
18. I think that each planet would move in a straight line at constant speed, because there will be a zero gravity condition and there won't any impact on the planets.
19. According to the Work-Energy Theorem we have:1/2*1200*2^2 = 2400 (J);Then let's count the average force according to the formula: Work = F*D where D is displacement.F = 2400/ 0.15 = 16000 (N)
So the answer is B. 1.6 × 10^4 N
20. If my memory serves me well, magnetism is the force that can act through empty space. It's one aspect of the combined electromagnetic force. So the answer is A.
21. According to the illustration given above, I think we should use formula F = m*g; Let's count m. m = 5 kg - 0,6 kg = 4,4 kg; Then we have everything to count force:F = 4,4 * 9,8 = 43,1 N. So the most approximate answer is D. 43 N.
22. I am definitely sure that the answer is C. on Earth at sea level. Because weight has the formula W=mg. And on the earth surface the magnitude of g is higher that everywhere so the greatest weight is on Earth at sea level.
23. We have everything to calculate the acceleration. According to Newton's second law, the formula is a = F/m;a = 20/40 = 0,5 m/s^2; So the answer is A.
24. According to the definition of action reaction forces, the answer should be: A. The forces are opposite in direction, with the force on the ball much stronger in magnitude.
25. I am pretty sure that we should use Newton’s second law of motion F = m*a. First we should find mass, using formula W=m*g => m = W/g => m = 2400/9.8= 245 kg. Then we can find F.F = m*a;F = 245*12 = 2940 N; Answer: B
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3 years ago

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