Physics problems, kneeling for answers and problem solving process

Joyful Song correction: t3 = v3 a3 = 12 8s =, answer: 1 The velocity of the object when the rope is broken is 8m s. 2. After the rope is broken, the object can also go up 4m 3, and the movement time from the beginning of the rope break to the object and then return to the bottom of the conveyor belt is t=t2+t3+t4=1+

n=mgcos37,f= n= n= mgcos37=,The friction is independent of the conveyor belt speed. 1. Before the rope is broken: uniform acceleration a1=(t-f-mgsin37) m==(10-2-1*10*,v1=a1t=8m s,s1=1 2a1t 2=1 2*2*4 2=after the rope is broken:

First decelerate evenly to rise to v2=0, and then accelerate down evenly. Note that the friction force is still downward when the velocity of the object is less than the speed of the conveyor belt. The deceleration rises to v2=0:

A2=(-F-Mgsin37) m=-8m s 2,t2=(v2-v1) a=1s,s2=v1 2 2a=4m up S1+S2=20m. Accelerate the slide evenly: The friction force is downward at the beginning of the slide, and if it is not at the bottom end after the slide is the same as the speed of the conveyor belt, the friction force will go up later.

Note: When judging the direction of friction, use the conveyor belt as a reference to see the relative direction of motion of the object, and f is opposite to the relative direction of motion. When you first started sliding:

A3=F+MGSin37) M=8M S 2, slide to the same speed as the conveyor belt v3=12m s,s3=v3 2 2a3=12 2 2*8=9m,t3=v3 a3=9 8s, then the friction force goes up, and then accelerates the downward trend:s4=s1+s2-s3=11m,a4=-f+mgsin37) m=4m s 2,v4 2-v3 2=28a4*s4,v4 2= (2*a4*s4+v3 2)= (2*4* 11+12 2)=, average velocity v'=(v3+v4) 2='=11 Answer: 1 The velocity of the object when the rope is broken is 8m s.

2. After the rope is broken, the object can still go up 4m 3. The movement time from the beginning of the rope break to the object and then back to the bottom of the conveyor belt is t=t1+t2+t3+t4=4+1+

Momentum is conserved, m1*v1=m2*v2

v1=m2*v2/m1=

That is, the backward speed of the machine gun.

Momentum theorem: the speed at which the machine gun retreats = the mass of the bullet * the speed of the bullet The mass of the machine gun =

The ground friction on the wooden block is (600+400).

The pulling force of the rope experienced by the person and the wooden block is half of the ground friction experienced by the wooden block, i.e., 200 2 = 100n

The frictional force experienced by the person is equal to the pulling force of the rope and is in the opposite direction, which is a pair of balancing forces, so the frictional force experienced by the person is 100N.

a=g 2So, the actual acceleration is.

a0=4a/5

v=√（2*

40√2（m/s）

t=√（2*400/

10√2（s）

Glide acceleration a=g*sin30-g*sin30*; (Multiplying both sides of the equation by m at the same time is better understood, and I can do this if I'm proficient).

v^2=2as=3200;

t=v/a;

I didn't play the straw paper at hand, so the landlord will count it himself.

The time interval between the two gunshots is 4s, which means that the first gunfire is heard for 4s and then the second gunshot, so the distance from the river bank to the cliff is x=340*4*1 2m=680m.

The other conditions are purely interfering conditions, do not be fooled.

Reflection of sound.

Exclude airborne transmission (by wearing vacuum earmuffs).

Vibration produces sound.

The sound travels in a straight line.

First of all, A released a shot, and what was heard was two sounds and 4s apart, so these 4s include its going sound and echo, and their distance is equal, so we first find the distance to the cliff: 340 s*4s 2=680m

Then he said that A and B are standing in a straight line from the river bank to the cliff, and they are 20m apart, so these 20m should be added, so in the end: 680m + 20m = 700m

After understanding the meaning of this question, when he moved 2m, the ball just moved upward, that is, after 1s, the ball went upward, according to the VO = per second.

According to mg=mv2r, obtained.

The velocity of the ball through the highest point of the arc orbit is at least v= (gr) and is conserved by mechanical energy:

mgh=mg2r+

h=Hope the above answer can be helpful to you