Efficiency of Air conditioner
someone designed an air conditioner that takes 500J of thermal energy from a cold room and exhausts 500J of thermal energy into the outside air. The energy is conserved, so the system should work. Is such a system feasible or are we optimistic about this new design. Why or why not?
asked praveen kumar
Categories: Ask Physics Tags: Air conditioner, Air conditioning, energy, Energy conservation, HVAC, Seasonal energy efficiency ratio, Shopping, Technology
Refraction – Disappearing letters
A rectangular block of glass is placed on a printed page lying on a horizontal table. what is the minimum value of u of glass so that the letters on page are not visible from any of the vertical faces of the block.
Asked Kushagr
Categories: Ask Physics, Interesting Questions, Optics Tags: Business, Crafts, Glass, Lens, light, Materials and Supplies, refraction, Shopping
Body at incline
1. In first case we have the box with weight, say, 10 Newtons on incline. We calculate two components (perpendicular and parallel)of weight. We calculate normal force and force of friction. The box is at rest.
2. In second case we have ball on incline, made of same material as box from first case. Weight of the ball is the same as in first case, components of weight are the same as in first case. Normal force and friction have the same amount as in the case of box. But,unlike the box, ball is moving – it slides down. How’s that possible? If calculated net force is zero?
Petar asked
Answer:
It is not true that the ball slides, but it will roll down.
In the first case, the forces balance each other and there is no motion.
In the second force, the frictional force acting tangentially backwards (up the incline) and the component of weight of the ball acting parallel to the plane and through the centre of the ball constitute a couple and tends to rotate it. Now there is no sliding; it rolls.
(If any further clarification is required please post as comment to this post)
Please refer to http://www.real-world-physics-problems.com/rolling-without-slipping.html for detailed treatment of the Physics of rolling without friction.
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Categories: Ask Physics, CBSE PHYSICS CLASS XI, Interesting Questions Tags: friction, gravitation, Health, India, Indian mathematics, Mathematics, Net force, Newton, Newton's laws of motion, Normal force, Shopping, Veda, weight, Weight Loss
Balancing a metre scale on two fingers –
When we place a scale balancing on our two fingers,why can’t we move them simultaneously, without the scale falling?
Answer:
We can! if the hands are not tilted and if the movement is without a jerk, the scale will not fall no matter how fast the fingers are moved.
This happens because, the centre of mass of the system is not changes because of the happenings within the system without the aid of any external agency.
Categories: Ask Physics, CBSE PHYSICS CLASS XI, Interesting Questions Tags: Bill Borger, load balancing, Models, Railroad, Recreation, scale, Shopping, Web server
