Distress! Physics bridging questions. Ask for help for physics questions!!

d, the elastic force must be two objects squeezing each other to produce deformation.

aAs long as it comes into contact, it will be deformed. Contact, on the other hand, cannot be all plastic deformation, nor can it be all elastic deformation.

bLack of contact conditions.

cBecause of the limitation of visual discrimination.

dLack of contact conditions.

So, do you know what to choose?

The elastic force is defined as follows: the deformed object has a force on the object in contact with it due to the fact that it is about to return to its original state, and this force is called elastic force.

aNot necessarily deformed.

b Not necessarily contact.

c. Deformation does not necessarily have to be restored.

d correct. I hope it helps, just read the definition.

Wrong choice of DA; Elastic force is the contact force, and the elastic force can only exist at the contact point of objects, but between objects that are in contact with each other, there is not necessarily the effect of elastic force. Because elasticity is generated not only by contact, but also by interaction.

B false; Elastic force is a contact force, and elastic force can only exist at the point where objects come into contact with each other.

c false; The deformation that can return to its original state after the external force has ceased to act is called elastic deformation. An object that undergoes elastic deformation exerts a force on the object that comes into contact with it and prevents it from returning to its original shape. This force is called elastic force.

d pairs; There is a definition of elasticity.

The change in shape of an object under the action of force is called deformation. The deformation that can return to its original state after the external force has ceased to act is called elastic deformation. An object that undergoes elastic deformation will exert a force on the object that comes into contact with it. This force is called elastic force.

The deformed object has a force on the object in contact with it because it is about to return to its original shape, and this force is called elastic force. Elastic force is the contact force, and the elastic force can only exist at the contact point of objects, but between objects that are in contact with each other, there is not necessarily the effect of elastic force. Because elasticity is generated not only by contact, but also by interaction.

So choose D.

d Only objects that are elastically deformed produce elastic force.

d. The condition for the elastic force to be generated is that it is in contact with each other and has extrusion.

If the net force of this object is what we want to f, according to the definition of work and the function theorem:

w = f·s = m·v² —0By substituting the numerical values, the mass and external forces can be easily calculated.

f = e s = w s = 3000 j 15 m = 200 n--- how much work is done by an external force, how much energy is consumed.

m = 2w/v² =6000 j ÷ 60 ÷ m/s)² kg

If the frictional resistance is not considered, in the whole process, only the force f does the work, that is, there is w=fx=15f=3 10 j, which can be obtained.

f=200n，60km/h=60/ m/s=50/3m/s

Let the acceleration be a, then there is v = v0 + 2ax, f = ma, where v0 = 0, v = 50 3m s, x = 15m, and the solution can be obtained by substituting m =

The question gives the energy and the velocity before and after.

From the formula of kinetic energy, it is easy to derive the mass.

And the energy is equal to the force multiplied by the displacement, knowing the displacement, the force is also easy to get.

Analysis: If the speed of the water flow is v water, the speed of the boat in still water is v boat, and the river width is h, then there is a problem to obtain.

v water * t1 = x, x = 120m, t1 = 10s, v water = 12m s, and h = v ship * t1 = v ship * sin * t2, can get sin = 4 5, so =arcsin4 5 = 53 °, and v ship * cos = v water, capacity.

v-ship = 20m s.

So h=v ship*t1=200m, so, the velocity of the current is 12m s; The speed of the boat in still water is 20m s; The width of the river is 200m; The angle between the bow and the river bank is 53°.

1.From the meaning of the title, it can be seen that the force analysis of the object, when the force f acts, the object is subjected to gravity, tension, friction, and decomposes the force along the inclined plane, there is a1=(160-60-200) 10, v1=a1*t1, after removing the tensile force, there is a2=(60+80) 10, and a2*t2=v1, the dynamic friction factor =, a1=5 m s 2, a2=8 m s 2.

Total displacement x=1 2*a1t1 2+1 2*a2t2 2= m

From the conservation of mechanical energy, there is: mgh = solution v = 10m s to obtain the resultant impulse i''=mv=20ns

and the resultant force f=mgsin30'=10n, support force f'=mgcos30'=10x3^

So t=i''/f=2s

So the gravitational impulse i=mgt=40ns

Support force impulse i'=f't=20x3^