Light travels faster than sound. So there is a difference
of seconds of time between seeing a flash and hearing a thunder.
speed of sound decreases with the increase in density of the medium. In rainy season, when the air is moist and its density is less, sound travels faster than in winter.
When a moving particle collides with a
stationary particle, part or full of the kinetic energy of the moving
particle is transferred to the stationary particle.
immersed the crown in water. He noted the difference in water levels to
find the volume of water displaced. He measured the weight by a
balance, using which he found the density of the crown. The pure gold crown is
denser and weighs more than impure crown as impurities such as silver,
copper are lighter than gold. He calculated the density of pure gold and density of gold in the crown.
Mechanical work = Force acting on an object * displacement of the object.
= torque acting on an object * angle through which object rotates
= the change in the kinetic energy of the object. (initial - final)
Its SI unit is Joules.
work means the system or the body does work. Negative
work means some external system or environment has done work on the
system or body.
If a body falls from a height then gravity does
work on the body. So the work done by the body is negative. So its
If a moving ball on a floor comes to rest, then the
work done by the ball is positive. So its energy decreases and final
kinetic energy is less than the initial.