Which statements about braking a car are true?
the greater the kinetic energy of a car, the longer it takes for the car to stop.
the lower the kinetic energy of a car, the longer it takes for the car to stop.
if the speed of a car doubles, the car’s kinetic energy and braking distance quadruple.
if the speed of a car doubles, the car’s kinetic energy and braking distance remain the same.

C. If the speed of a car doubles, the car’s kinetic energy and braking distance quadruple. And A.The greater the kinetic energy of a car, the longer it takes for the car to stop.

The greater the kinetic energy of a car, the longer it takes for the car to stop.

If the speed of a car doubles, the car’s kinetic energy and braking distance quadruple.

Explanation:

The kinetic energy is given by the formula,

½ mv²

where m is the mass and v is the velocity.  

So when the velocity or speed doubles the kinetic energy will quadruple.  

A car moving with high kinetic energy has a high speed or velocity therefore it is going to take more time to reduce the higher speed and bring the car to a halt.  

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2