Urgent Urgent Senior 1 Physics Questions

1 The displacement of an object falling in the first two seconds is 20 meters.

The average power is the work done by gravity divided by time.

p=5*10*20/2=500w

2. Instantaneous power refers to the force * instantaneous velocity.

p=5*10*10*2=1000w

1)p=fh/t=mg(1/2gt^2)/t=1/2mg^2t=1/2*5*10^2*2=500w

2) p = fv = mg * gt = 5 * 10 * 10 * 2 = 1000w power is the work done per unit time, work = force * distance moved in the direction of force.

Power is also equal to force multiplied by velocity. p=fs t=f(s t), s t is the velocity, so p=fv

We don't have this kind of question in our first year of high school!! - Do it and try it.

p=w/t=gh/t=mgh/t

h=1/2*gt^2=20m

p=5*10*20/2=500w

Instant power = 0

Hello. Here's how:

Because the relative speed of the boat and the lifebuoy remains the same (that is, the speed of the boat itself remains the same), the speed of the boat away from the lifebuoy is the same as the speed close to the lifebuoy, then the time from finding the lifebuoy falling into the water to picking up the lifebuoy is also t, adding up to a total of 2t time from the lifebuoy falling into the water to picking up the lifebuoy.

At this time, the lifebuoy goes x in the water, because the water flow speed is the lifebuoy drift speed, so:

The water velocity is x 2t

You can also solve the equation in a row, if you don't know, you can ask me again.

(1)c

2) You should have calculated the instantaneous velocity, as for the second space, you can calculate the velocity of 345 points, draw the image, and the slope k is the acceleration.

Or x=at can also be calculated.

At point 4, the instantaneous speed of the trolley is v4

At point 5, the instantaneous speed of the trolley is v5

The acceleration of the trolley is.

v5-v4)/t

t should be more or less understood.

thanks

Classmates, why don't you have time, how can you calculate speed if you don't have time!!

This is mainly the conversion of the circular motion formula of the gravitational force formula:

gmm/r²=mv²/r。Simplify to obtain v1= gm r

Then the first cosmic velocity of the planet v2= g4m (r 2) = 8gm r = 8 v1 = 2 2 v1.

Thank you.

The first cosmic velocity is the minimum velocity of the flight around the earth, that is, the centripetal acceleration around the earth with g. The formula of centripetal acceleration can be expressed as a=v 2 r, and the formula for calculating g is g=g*m r 2, and the two are equal, that is, v 2 r = g*m r 2, and v 2 = g*m r

So the square of this velocity is directly proportional to the mass of the planet and inversely proportional to the radius of the planet.

The ratio of the square of this velocity on a planet to the square of this velocity on Earth is 8, so the velocity is 2 2 times the velocity on Earth, i.e. 2 2v1

The first cosmic velocity of the earth is v1, that is, the orbital velocity of the projectile on the surface of the earth is set to the radius of the earth r1, the mass of the earth m1, and the mass of the flying object m, then the centripetal force gm1m r1 2=mv1 2 r1 can be seen according to the gravitational force: v1 = under the root number (gm1 r1).

Imitated on the Earth: the radius of a planet r2 = (1 2) r1, the mass of a planet m2 = 4m1, the first cosmic velocity of the planet v2 = under the root sign (gm2 r2) = under the root number (8gm1 r1).

gmm/r^2=mv^2/r

v = root number (m r).

So v=2 root number 2 times v1

where g m is eliminated when solving the problem, and the difference between the earth and a planet is the mass m and the radius r

11.A car enthusiast who was planning to go sightseeing in a scenic area with an almost straight road between the starting point and the destination was planned to reach an average speed of 40 for the whole journey

km h, if this tourist enthusiast drives 1 3 and finds that his average speed is only 20 km h, will he be able to complete the plan with an average speed of 40 km h? If so, how fast should he be required to drive for the next 23 miles?

Analysis: Let the average velocity on the last 23 distances be v, and the total distance is s in the first 3 miles: t1=s 320

Time spent in the last 2s 3: t2=2s 3v

Therefore, the average speed of the whole journey is: ss60+2s3v=40km h, and the solution is v=80

KMH shows from the results that the traveler was able to complete his plan, and he should reach a speed of 80 in the last 2s 3

km/h.Answer: 80

km h sit down with this question!