The distance covered by car is equal to (assuming it is moving by uniform motion) the product between the car's speed and the time of the car ride, 4 h:

where

is the car's speed

is the duration of the car ride
Similarly, the distance covered by train is equal to the product between the train's speed and the duration of the train ride, 7 h:

The total distance covered is S=255 km, which is the sum of the distances covered by car and train:

which becomes

(1)
we also know that the train speed is 5 km/h greater than the car's speed:

(2)
If we put (2) into (1), we find

and if we solve it, we find


So, the car speed is 20 km/h and the train speed is 25 km/h.
Answer:
F=m*g is the formula and the answer is 19,620 kg
Explanation:
Since the formula is F=m*g and Earth's gravity is 9.81 m/s^2 all you need to do is multiply 2,000 by 9.81
Answer:
2.6×10⁻³ N
Explanation:
From coulomb's law,
F = kq'q/r²................ Equation 1
Where F = Repulsive force, q' = charge on the first sugar grain, q = charge on the second sugar grain, r = distance of separation between the sugar grain, k = proportionality constant.
From the question,
since q' = q
Then,
F = kq²/r²..................... Equation 2
Given: q = 1.79×10⁻¹¹ C, r = 3.45×10⁻⁵ m,
Constant: k = 9×10⁹ Nm²/kg².
Substitute into equation 2
F = 9×10⁹(1.79×10⁻¹¹)²/(3.45×10⁻⁵ )²
F = 9×10⁹(3.2041×10⁻²²)/(11.9025×10⁻¹⁰)
F = (28.8369×10⁻¹³)/(11.9025×10⁻¹⁰)
F = 2.6×10⁻³ N.
The speed of a proton after it accelerates from rest through a potential difference of 350 V is
.
Initial velocity of the proton 
Given potential difference 
let's assume that the speed of the proton is
,
Since the proton is accelerating through a potential difference, proton's potential energy will change with time. The potential energy of a particle of charge
when accelerated with a potential difference
is,

Due to Work-Energy Theorem and Conservation of Energy - <em>If there is no non-conservative force acting on a particle then loss in Potential energy P.E must be equal to gain in Kinetic Energy K.E</em> i.e

If the initial and final velocity of the proton is
and
respectively then,
change in Kinetic Energy 
change in Potential Energy 
from conservation of energy,

so, 

To read more about the conservation of energy, please go to brainly.com/question/14668053
Answer:
Chemical composition, Temperature, Radial velocity, Size or diameter of the star, Rotation.
Explanation:
Elemental abundances are determined by analyzing the relative strengths of the absorption lines in the spectrum of a star.
The Spectral class to which the star belongs gives the information related to the temperature of the star. It is the spectral lines that determine the spectral class O B A F G K M are the spectral classes.
By measuring the wavelengths of the lines in the star's spectrum gives the radial velocity. Doppler shift is the method used to find the radial velocity.
A star can be classified as a giant or a dwarf . A giant star will have narrow width spectral lines whereas a dwarf star has wider spectral lines.
Broadening of the spectral lines will determine the star's rotation.