Advertisements
Advertisements
प्रश्न
How much energy is gained by a box of mass 20 kg when a man, carrying the box waits for 5 minutes for a bus?
Advertisements
उत्तर
Mass of box = 20 kg
t = 5 minutes
Energy gained = force applied = 0
∵ Zero work is done, as there is no displacement of the man.
APPEARS IN
संबंधित प्रश्न
State the S.I. unit of energy.
Explain degradation of energy by taking two examples of your daily life.
Name five appliances or machines which use an electric motor.
Does the earth move around the sun with a uniform velocity?
No work is done by a man moving on a horizontal road while carrying a box on his head. Explain.
A body does 20 J of work in 10 s. What is its power?
A man climbs a slope and another walks same distance on level road. Which of the two expends more energy and why?
A truck driver can load oil drums into the back of the truck by pushing them up a sloping plank, or by lifting them directly. Each drum has a mass of 80 kg, the plank is 3 m long, and the back of the truck is 0.8 m above the ground.
(i) How much force would be needed to lift a drum into the truck directly/without using the plank? (Take g = 10 m/s2)
(ii) How much energy would be required in lifting the drum into the truck without the plank?
(iii) If the force needed to push the drum up the plank is 300 N, why is this less than the answer to part (i)?
(iv) When the truck is loaded, the driver drives off. List the major energy changes that take place in moving the truck.
(v) The driver has to stop at the factory gates. What happens to the kinetic energy of the truck?
