Detailed analysis of the answers to the first year of high school summer vacation homework physics c

1.There seems to be an error in the data.

Let be: when passing through point b, the velocity of the object is v; The inclined plane of gravity transformation is constant with f, and the deceleration is constant with a.

Due to the smooth bevel, f-friction = 0 n

From the momentum theorem, f·t = m· ( v)：

vab = 2v - v = v = vbc, m unchanged, f unchanged tab = tbc = s

sab = a·t^2 / 2 ∴a = 2sab / t^2 = 6 m/s^2

In this case, if you want to pass through the AB two points, the initial velocity of the object must be greater than 6m s. Data errors.

To conform to the inscription, the object can only start between the slopes of AB and then pass through A on the way down.

In this way, the slope length and the time from the bottom of the slope to B cannot be determined unless the slope is at point A.

2.First, change the unit of velocity to m s — v = 36 10 3 3600s = 10 m s

From the momentum theorem f·t = m· v, we get: f = m· (2v) t = 10000 m

And the force experienced in the acceleration of death is: FO = 500g·m = 5000 m

f fo, the driver's life is in danger.

The data is correct, and I'll tell you the first question.

va=2vb, 4vb^2-vb^2=2axab,(1) vb-at=0.(2) From 1,2 biqs a=2m s 2 vb=1m s 2ax oblique = v0 2 x oblique = 4m t=(vb-v0) -a= end,,thank you.

Answer: 1:2;1/2v0t0；4:1

Analysis: According to the momentum theorem, ft = mv, in the process of relative motion of a and b, their combined external forces are equal, and the ratio of the change in velocity is 2:1, so the ratio of mass is 1:

2；The minimum length of b is equal to the difference between the displacements of a and b in the process of relative motion, and the difference between the displacements of a and b is equal to the area of the triangle in the figure s=1 2v0t0; From the kinetic energy theorem, it can be seen that the work done by the resultant external force is equal to the amount of change in the kinetic energy of the object, and in this problem, the combined external force for a and b is equal to the frictional force, so the ratio of the work done by the frictional force is equal to the ratio of the change in the kinetic energy of the object, which is 4:1.

Solution: (1) The effect of the work done on the ball when a person throws the ball is to let the ball have a certain speed, that is, the speed of the ball increases from 0 to 12m s

According to the kinetic energy theorem: man does work w=mv 2-0

Substituting m=, v=12m s to get w=

2) If the air resistance is not counted, the mechanical energy of the ball is conserved, according to the law of conservation of mechanical energy MV1 2=MGH+MV2

Substituting m=, v=12m s, h=, g=10m s to obtain v1=14m s

A: 1Man only does work on the ball at the moment of throwing, and the magnitude of this work is equal to the initial kinetic energy of the ball: w=1 2mv 2=1 2*

2.Let the final velocity of the ball when it lands be v', which is obtained by the kinetic energy theorem: 1 2mv' 2-1 2mv 2=mgh

h= v=12m s as long as v is calculated'Can.

Or conservation of energy: 1 2mV'2=mgh+1 2mv 2 also gives v'=14ms

People work on qiu, do not add gravity work, so; 1/

Without calculating the resistance, the mechanical energy is constant, mgh=1 2m(v2 2-v1 2).

v2=14m/s

This question is a complete investigation of the kinetic energy theorem, which can be made by applying the kinetic energy theorem. The initial velocity of the ball is to do work on the ball, and the final kinetic energy is the addition of the initial kinetic energy and the gravitational potential energy, and then the velocity is calculated according to the kinetic energy formula.

The topic is your own.

Do the functional kinetic energy theorem, w=1 2mv2=1 2*

The gravitational workmanship is equal to the change in kinetic energy, 1 2mv end 2-1 2mv2=mgh

End of v = 14 m s

The rate of change of magnetic flux in a multi-turn coil is . How many turns are needed to make the induced EMF spike generated in the coil?

From the formula e=n (δt) we get:

n=e (δt)= turns.

2.A coil has 75 turns and an area of cm squared. The coil is moved between the poles of the magnet and the coil is shifted between the poles of the magnet from the magnetic induction, and the voltage at both ends of the coil is large?

If there is a 10 ohm resistor at both ends of the coil and the internal resistance of the coil is ohms, how much current is generated in the circuit?

1) e==n•(δt)=n•b•δs/δt=2) i=e/r=

3。In a magnet with b=, a copper rod with a length of 15 cm moves perpendicular to the direction of the magnetic field at a velocity, and the magnitude of the induced electromotive force in the rod is found.

e=blv=

Let the time be t and the acceleration is a, then according to v 2 2a = s80km h = 200 9m s, 48km h = 40 3m s so (200 9) 2 2a = 56-200t 9 (40 3) 2 2a = 24-40t 3

From the above two equations, it can be solved: t=

It looks so familiar, I just finished it yesterday

What page is that? Why didn't I find it?

You pass first. v0t1+v0t2+1/2at2^2=56v't1+v't3+1 2at3 2=24 It doesn't seem to work

In this way: 80t1 + 40t2 = 56 * 10 -348t1 + 24t3 = 24 * 10 -3

t2:t3=80:48

t1 is the reaction speed.

T2 is the time it takes to brake for the first time.

T3 is the second time.

Moment balance problems. The top of the rod is used as the axis of rotation.

Let the angle between the rod and the horizontal direction be , and the dynamic friction factor between the rod and the wooden block is N*LCOS =G*(L2)COS when left: N1*LCOS (N1)*LSIN =G*(L 2)COS

To the left: N2*LCOS - (N2)*LSIN = G*(L2)COS

Eliminate , solve: n2=

Anyone can do quick writing, I'm also in a hurry. Please!!

Rotational speed n=30r min, then angular velocity 30 2 60

It is obtained by the maximum static friction force of f and the centripetal force of f.

r (2) m.

Solution: (1) Particle: accelerates in the electric field, known by the kinetic energy theorem.

u1q = solution v= (2u1q m).

2) Particle: In the velocity selector, the electric field force is balanced with the Lorentz force, which is known by the equilibrium condition b1qv=eq,e=u2 d

The solution gives u2=b1qdv=b1qd (2u1q m)(3) particles: in a deflection separator, the Lorentz force acts as a centripetal force, known by Newton's second law b2qv=mv 2 r

The solution is r=mv b2q=[ (2u1m q)] b2

(1) Acceleration from 0 in the accelerator.

u1q=mv^2/2

2) Since the velocity selector can be passed, the Lorentz force and the electric field force balance b1qv=u2q d

3) The Lorentz force provides the centripetal force.

b2qv=mv^2/r

Senior 2 Physics Questions: See the attachment for details, I hope the teacher of the width of life will answer them.