As a ball rolls ... even if there were no air resistance ... the ball
has to push down and climb over every one of those little fibers
that stick up from the felt fabric on the table. As it does that, each
little fiber brushes against the ball, and robs a tiny tiny bit of its
kinetic energy.
What you want to test and your hypothesis does.
For example, say you came up with a hypothesis that 'The higher the temperature, the higher the reaction rate will be'.
Your independent variable (the one you change) will be temperature. The dependent variable (the one that changes because of the independent) will be the reaction rate (e.g. bubbles produced).
Explanation:
It is given that,
Radius of curvature of the mirror, R = 1.54 cm
(a) We have to find the focal length of the mirror. The relationship between the focal length and the radius of curvature is given by :
f = focal length of the mirror
f = 0.77 cm
(b) The power of mirror is given by the reciprocal of focal length i.e.
Power, 
P = 1.29 diopters
Hence, this is the required solution.
Answer: 9.9%
Explanation: efficiency = (work output /work input) × 100
Note that, 1 kilocalorie = 4184 joules, hence 22kcal = 22× 4184 = 92048 joules.
Work output = 9200 j and work input = 92048 j
Efficiency = (9200/92048) × 100 = 0.099 × 100 = 9.9%
On a speed/time graph, the height of the line at any point
shows the speed at that moment. If the line is horizontal,
then its height isn't changing, meaning that the speed isn't
changing. It's constant. The change is zero, until the line
starts rising or falling.
