One physics question, one physics question

Analysis: Let the initial velocity of the ball when it is thrown vertically be v0, if the air resistance is not counted, then v v0 gt

Kinetic energy of the ball:

ep＝½mv²＝½m(v0－gt)²

When the ball is at its highest point, v 0

t＝v0/g

Obviously, ep 0

The image as a function of kinetic energy over time is hyperbola.

If you're just writing about relationships, you don't need to think about what acceleration. After all, acceleration is the content of high school.

1.Xiao Ming throws a small ball straight up, and the ball moves in the air after leaving his hand.

As the potential energy increases during the ascent, the kinetic energy becomes smaller and smaller according to the conservation of mechanical energy. Until the kinetic energy is 0, i.e., the entire kinetic energy is converted into potential energy. Therefore, the relationship between the kinetic energy of the ball and time is: with the increase of time, the kinetic energy becomes smaller and smaller.

2.Tom throws a small ball straight upwards from the time the ball leaves his hand until it finally lands on the ground.

As can be seen from the above question, the kinetic energy decreases until it reaches 0, and all of it is converted into potential energy. The object with potential energy falls downward, converting the potential energy into kinetic energy. So, the kinetic energy gets smaller first and then increases with time.

What school do you have? Running the school mechanics so soon?

1. The kinetic energy is constantly decreasing.

2. The kinetic energy continues to decrease, and when it reaches the highest point, the kinetic energy is 0, and then it continues to increase.

The magnitude of kinetic energy depends on the mass and velocity, the greater the velocity of an object with a certain mass, the greater the kinetic energy, and when the velocity is 0, the kinetic energy is 0.

It's wrong that you still regard the force of the motor behind as 5N, before the speed of A reaches 1m s, the force is 5N, because the speed of B has always been 1m s, but when A and B accelerate together after the same speed, this force changes, because the power is maintained is 5W, so there is f*v==5, when the speed changes the force, it also changes, so the later stage is not a uniform acceleration motion but a variable acceleration motion, and the speed time diagram in the back period is not a straight line but a curve, and you will not find the area, you have to use calculus to find it. Therefore, this problem can only be solved by conservation of energy in high school.

1.Stick to a let the speed of the bucket up.

Momentum is conserved. mv1+mv2=（m+m）v3

v3＝2.Mechanical energy is not conserved.

The initial energy is. 1 2 (MV1 2 + MV2 2) Tan Bei Mo 1 2 (

The last kinetic energy. 1/2（m+m）v3^2

The energy loss is 20000-16000 4000J The initial kinetic energy is not equal to the final kinetic energy, and the mechanical energy is not conserved.

100 meters stop.

s＝1/2at^2 ＝100

t＝v/a＝

The rolled pin is s

A side. f＝ma=2*25000*

It is also possible to 16000 100f f = 160n

Hehe, I'd like to help you answer, but my English is not good, I'm sorry.

A 2 cars have the same mass and the same speed direction. v=（v1+v2）/2=

b None. After a collision, the energy reduced by the car with the higher speed is used to increase the energy of the car with the lower speed. Reduces the energy of the trip to the energy lost in the collision.

c s=100m.m=25000*2= f=ma s=1 2at 2+vt I dismantled the world and returned to the cave without a pen, so let's solve it myself.