Advertisements
Advertisements
प्रश्न
A person of mass 60 kg wants to lose 5kg by going up and down a 10 m high stairs. Assume he burns twice as much fat while going up than coming down. If 1 kg of fat is burnt on expending 7000 kilo calories, how many times must he go up and down to reduce his weight by 5 kg?
Advertisements
उत्तर
Given, the height of the stair = h = 10 m
The energy produced by burning 1 kg of fat = 7000 cal
∴ The energy produced by burning 5 kg of fat = 5 × 7000 = 35000 kcal
35 × 106 cal
The energy utilised in going up and down one time
= `mgh + 1/2 mgh`
= `3/2 mgh`
= `3/2 xx 60 xx 10 xx 10`
= 9000 J
= `9000/4.2`
= `3000/1.4` cal
∴ A number of times, the person has to go up and down the stairs
= `(35 xx 10^6)/(3000/1.4)`
= `(35 xx 1.4 xx 10^6)/3000`
= 16.3 × 103 times
APPEARS IN
संबंधित प्रश्न
In changing the state of a gas adiabatically from an equilibrium state A to another equilibrium state B, an amount of work equal to 22.3 J is done on the system. If the gas is taken from state A to B via a process in which the net heat absorbed by the system is 9.35 cal, how much is the net work done by the system in the latter case? (Take 1 cal = 4.19 J)
Should the internal energy of a system necessarily increase if heat is added to it?
Should the internal energy of a system necessarily increase if its temperature is increased?
A cylinder containing a gas is lifted from the first floor to the second floor. What is the amount of work done on the gas? What is the amount of work done by the gas? Is the internal energy of the gas increased? Is the temperature of the gas increased?
When we rub our hands they become warm. Have we supplied heat to the hands?
A closed bottle contains some liquid. the bottle is shaken vigorously for 5 minutes. It is found that the temperature of the liquid is increased. Is heat transferred to the liquid? Is work done on the liquid? Neglect expansion on heating.
When a tyre bursts, the air coming out is cooler than the surrounding air. Explain.
Refer to figure. Let ∆U1 and ∆U2 be the changes in internal energy of the system in the process A and B. Then _____________ .
Consider two processes on a system as shown in figure.
The volumes in the initial states are the same in the two processes and the volumes in the final states are also the same. Let ∆W1 and ∆W2 be the work done by the system in the processes A and B respectively.
A gas is taken along the path AB as shown in figure. If 70 cal of heat is extracted from the gas in the process, calculate the change in the internal energy of the system.
A system releases 130 kJ of heat while 109 kJ of work is done on the system. Calculate the change in internal energy.
Which of the following system freely allows the exchange of energy and matter with its environment?
What is the internal energy of the system, when the amount of heat Q is added to the system and the system does not do any work during the process?
Explain given cases related to energy transfer between the system and surrounding –
- energy transferred (Q) > 0
- energy transferred (Q) < 0
- energy transferred (Q) = 0
When 1 g of water at 0° C and 1 x 105 N/m2 pressure is converted into ice of volume 1.082 cm3, the external work done will be ____________.
Which of the following represents isothermal process?
In thermodynamics, heat and work are ______.
An expansion process on a diatomic ideal gas (Cv = 5/2 R), has a linear path between the initial and final coordinates on a pV diagram. The coordinates of the initial state are: the pressure is 300 kPa, the volume is 0.08 m3 and the temperature is 390 K. The final pressure is 90 kPa and the final temperature s 320 K. The change in the internal energy of the gas, in SI units, is closest to:
The molar specific heat of He at constant volume is 12.47 J/mol.K. Two moles of He are heated at constant pressure. So the rise in temperature is 10 K. Find the increase in internal energy of the gas.
What is heat?
