Answer:
(a) 3.13 m/s
(b) 9.9 m/s
(c) 7.73 m/s
Explanation:
u = 0 m/s, g = 9.8 m/s^2
Let v be the velocity of ball as it hit the ground.
(a) h = 0.5 m
Use third equation of motion.
v^2 = u^2 + 2 g h
v^2 = 0 + 2 x 9.8 x 0.5
v^2 = 9.8
v = 3.13 m/s
(b) h = 5 m
Use third equation of motion.
v^2 = u^2 + 2 g h
v^2 = 0 + 2 x 9.8 x 5
v^2 = 98
v = 9.9 m/s
(c) h = 10 feet = 3.048 m
Use third equation of motion.
v^2 = u^2 + 2 g h
v^2 = 0 + 2 x 9.8 x 3.048
v^2 = 59.74
v = 7.73 m/s
Answer:
Acceleration=velocity/time.
=80/2=40m/s^2.
Answer:

Explanation:
As we know that 1 lb fat can be used to expend 4.1 k Calorie of energy
so here we know that we have to use 7.56 lb of body fat
so here the total energy that is to be utilized is given as

so we will have

now we know that runner expends the energy at rate of 1850 kJ/h
so we have

so it is

now we know that time to burn this energy is given as



Answer:
Explanation:
Since X-rays are high (energy) frequency photons and radio waves are composed of low (energy) frequency photons, X-rays are more energetic and can do more harm to organic materials (such as cells).
This would be more of a chemistry question. Remember magnesium has a charge of 2+, and would need to hand off its two extra electrons. Fluorine can only take one electron at a time, so there needs to be two fluorines to take one magnesium's 2 electrons.
With lithium, it has a +1 charge, so it has one extra electron, which it can hand off to just 1 fluorine atom.
Another way of looking at this is:

+ 2

= MgF2 (the charges must balance out to zero)

+

= LiF (the charges balance out to zero)