Ncert Exercises & Solutions

Q.42. An adult weighing 600 N raises the center of gravity of his body by 0.25m While taking each step of 1 m length in jogging. If he jogs for 6 km, calculate the energy utilized by him in jogging assuming that there is no energy loss due to friction of ground and air. Assuming that the body of the adult is capable of converting energy intake in the form of food, calculate the energy equivalents of food that would be required to compensate energy utilized for jogging.

Hint: Total energy utilised in jogging = total number of steps x mgh.

Step 1: Find total number of steps.

Given, weight of the adult (w) = mg = 600 N

Height of each step = h = 0.25 m

Length of each step = 1 m

Total distance travelled = 6 km = 6000 m

∴ Total number of steps = \frac{6000}{1} = 6000

Step 2: Find total energy utilised in jogging.

Total energy utilised in jogging = n x mgh

= 6000 x 600 x 025J = 9 x 10⁵ J

Step 3: Find total intake energy.

Since, 10% of intake energy is utilised in jogging.

∴

Total intake energy

\times \frac{10}{100}

= x 9 x 10⁵ J

∴

Total intake energy = 10 x 9 x 10⁵ J = 9 x 10⁶ J.

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