Explanation:
Principle focus is the point on the axis of a convex lens, where the parallel rays of light from one side of the lens. meet on other side after refraction. Distance between optical centre to principle focus point is the focal length.
Answer:
FALSE
Explanation:
Velocity = speed with direction.
Think of speed and direction like rockets and missiles. Rockets are not smart. Missiles are smart. Rockets go in one direction. Missiles can track their targets, they have a specific destination, a specific direction.
Velocity is often used in physics, because its almost useless to know how fast an object is going if you don't know which direction it is going.
Think of it like this. If the Weather man told you a hurricane was traveling at 30 miles an hour, but didn't tell you which direction it was going, you would have no idea where to run, or if it was going to hit you at all. However, if he told you it was going 30 miles an hour to the North, and you were West of it, you would be fine, and wouldn't have to worry.
The answer is:
C. 361 m/s
The explanation:
To calculate the speed of sound at a given temperature (50°C) we are going to use this formula:
v = 331 + 0.6T
when V is the velocity
and T is the temperature = 50°C
by substitution:
v = 331 + 0.6(50)
v = 361 m/s
So, The correct answer is C.
because of the variation of the motion of the molecules of air with change of temperature so, the velocity (V) of the sound in the air is change with temperature.
The crate moves at constant velocity, this means that its acceleration is zero, so the net force acting on the crate is zero (Newton's second law).
There are only two forces acting on the crate: the force F applied by the worker and the frictional force, acting in the opposite direction:
, where
is the coefficient of friction and
is the mass of the crate. Since the net force should be equal to zero, the two forces must have same magnitude, so we have:
And so, this is the force that the worker must apply to the crate.
