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How long does it take for an object to reach the midpoint of a smooth slope? (know that the length of the inclined plane is l, the final speed is V, and the speed at the midpoint of the inclined plane is v / radical 2) We also know that the time that the object passes through the inclined plane is t, please use t to express the answer
Square of final velocity - square of initial velocity = 2As
V^2-(V^2)/2=2a(L/2)
a=(V^2)/2L
The starting velocity is also calculated by this formula
（V^2)/2-V0^2=2a(L/2)=（V^2)/2
V0=0
Vt=V0+at
T = (vt-v0) / a = (V / root 2) / ((V ^ 2) / 2L) = root 2 * (L / V)
Put a plastic ball with a volume of 100cm3 into a cup filled with water and float on the water. The volume of boiled water is 80cm3. The pressure on the bottom of the cup is lower than the original pressure_________ (filling increases, remains unchanged, decreases) It's the pressure of the liquid on the bottom of the bottle, which is related to the depth and density
Oh, My God
Please look at the topic upstairs
It is a "cup full of water", so when the ball is put in, the water overflows and the water surface height does not change; Because the volume of boiled water is smaller than its own volume, it is floating without sinking
So, for the bottom of the cup, the height of the water surface remains the same, so the pressure remains the same. It's so simple!
… Throw five small balls vertically at the same speed every equal time, regardless of air resistance. When the first small ball reaches the maximum height, the fifth small ball is being thrown, and the first and second small balls are 0.2m apart. Find the initial speed of throwing the small ball. Please give the answer
When the first small ball reaches the maximum height, the first and second small balls are 0.2m apart, so the time interval t between throwing two adjacent balls can be calculated: T = 0.2S from H = (1 / 2) GT ^ 2 = 0.2m
The first ball reaches the highest point after 4T, and the acceleration is - g = - 10m / S ^ 2, so the initial velocity v = 4gt = 0.8m / S ^ 2
1. - the object surface can reflect parallel incident light in the same direction. The reflected light is parallel, which is called specular reflection ___ The object surface directs the parallel incident light to___ Reflection is called diffuse reflection Both specular and diffuse reflections follow___ The image of the moon can be seen under the water surface of a washbasin, which is due to the distance from the image of the moon to the water surface___ Distance from the moon to the water surface (fill = greater or less than) 3 the included angle between the reflected light and the plane mirror is 15 °. If the plane mirror is rotated to reduce the incident angle by 15 °, the included angle between the reflected light and the incident light is___ ° 4. The water depth of the river is 5 meters, and there are birds flying 15 meters away from the river. The image distance and surface of birds in the river___ rice 5. The light blocking slants from the air to the horizontal desktop, and the propagation direction___ (fill in certain or not necessarily) change the reflection angle___ (fill = greater than or less than) 6 a beam of light shines vertically on the plane mirror. If the direction of the incident light is not changed and the mirror is turned at an angle of 25 °, the change angle of the reflected light is___ 7. The calm water reflects the reflection of the mountain, which is the _. When swimming, you can see the fish in the water, which is the _ line propagation or reflection of light)
Reflection law of light in all directions
The reflection of light is equal to
3 120
4 15
5. The landlord must not have finished this space. Maybe it is "equal to the incident angle"
6 50
7 reflection phenomenon
The distance between the two places is 192.5km. There are two cars, a and B, starting from the two places at the same time. The speed of a is 25 km / h. The speed of B is 30 km / h Km / h. ask: (1) how long does it take for the two cars to meet after they leave? (2) The distance traveled by the two cars when they met In blasting, the burning speed of the fuse is 1cm / s and the running speed of people is 8m / s. if people can run to a safe area 160 meters away after igniting the fuse, find the speed of the fuse I'd like to list the formulas. Who can answer them? Thank you very much. I'm not good at physics
1. (1) time when two vehicles meet t = s ÷ v = 192.5km ÷ (25km \ H + 30km \ h) = 3.85h
(2) A: distance S = h × v=3.85h × 25km\h=96.25km
B: distance S = h × v=3.85h × 30km\h=115.5km
2. It's the length of the fuse. Your question is wrong
Fuse length s = h × V = s ÷ V persons (to be written in small letters) × V fuse (ditto) = 160m ÷ 8m \ s × 1cm\s=20s × 0.01m\s=0.2m
I'm from the third day of junior high school. I still remember some physics in the second day of junior high school, but don't blame me for being wrong. I don't have any points... For the sake of my hard answer, give some at least
The pressure of a 5-ton crawler tractor on the horizontal ground is about 3 × 104 PA, what is the contact area between each track and the ground? (g = 10 N / kg)
It can be seen from the meaning of the question that the pressure of the crawler tractor on the horizontal ground is its own gravity,
I.e. f = g = mg = 5000kg × 10N/kg=5 × 104N，
The pressure on the horizontal ground is about 3 × 104pa, according to the pressure formula P = f
s，s=F
P=5 × 104N
three × 104Pa=5
3m2．
A crawler tractor has two tracks, so the contact area between each track and the ground is 5
3m2 × one
2=5
6m2=0.83m2．
Answer: the contact area between each track and the ground is 0.83m2
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