A load of 35 N attached to a spring hanging
vertically stretches the spring 8.1 cm. The
spring is now placed horizontally on a table
and stretched 12 cm.
What force is required to stretch it by this
amount?
Answer in units of N

51.85 N

Explanation:

when hanging vertically,

mg = k*x  so we get k = mg/x = 35/8.1  N/cm

now for x = 12cm, we have to calculate F,

so F = k*x =  35/8.1 * 12 = 51.85 N

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.