thanks for solving my question pasted on dated 18.02.2011 at 10.20.pm.2nd question. a wt lifter lifts a wt of one kg against force of gravity through a distance of .8 mtr. how much cals he will burnt from the food he had taken.

What is your question about how to do this?

m g h = work done

If you use
1 kg * 9.8 m/s^2 * .8 m
your result will be in Joules
convert Joules to calories
You will then probably want to divide that result by 1000 because the calories we usually use for food are in fact kilocalories.

To calculate the calories burned by a weightlifter, we need to know the work done during the lifting process. Work is defined as the force applied to an object multiplied by the distance over which the force is applied.

In this case, the weightlifter lifted a weight of 1 kg against the force of gravity through a distance of 0.8 meters. We can determine the work done using the formula:

Work (W) = Force (F) x Distance (d)

The force exerted by the weightlifter is equal to the weight of the object being lifted, which is 1 kg multiplied by the acceleration due to gravity (9.8 m/s^2):

Force (F) = Mass (m) x Acceleration due to gravity (g)
F = 1 kg x 9.8 m/s^2
F = 9.8 N (Newtons)

Now we can calculate the work:

W = F x d
W = 9.8 N x 0.8 m
W = 7.84 Joules (J)

To convert the amount of work done into calories burned, we can use the conversion factor: 1 calorie = 4.184 Joules.

Calories burned = Work (in Joules) / Conversion factor

Calories burned = 7.84 J / 4.184 J/cal
Calories burned ≈ 1.87 calories

So, the weightlifter would burn approximately 1.87 calories from the food they had consumed in order to lift the 1 kg weight through a distance of 0.8 meters against the force of gravity.