Answer:
Because the sound travels faster in solids
Explanation:
Sound waves are mechanical waves, produced by the oscillations of the particles in a medium. The particles vibrate back and forth along the direction of propagation of the wave (longitudinal waves).
The speed of a sound wave depends on several factors, such as the density of the medium. In particular, the higher the density, the higher the speed of the wave, because in denser mediums the particles are more close to each other, so the transmission of the wave is more efficient since it can be transmitted better through the colliding particles.
For this reason, a sound wave travels faster in solids, and slower in gases.
Therefore in this problem, the sound of the oncoming train travels faster through the rail track (which consists of solids), rather than the air (which is a gas), so by putting the ear next to the track, it is possible to hear the sound of the train coming before the sound is heard in air.
You know now that 1200 km is 11° of latitude on the planet. So its circumference is roughly approximately around something like about
(360/11) • (1200 km) = 39,273 km
If it was good enough for Eratosthenes, then we can't complain.
Answer: A spanner with a long handle
Explanation: The use of a spanner for opening the nut of a simple machine will employ the principle of moment.
The force apply to the nut is considered as load while the force applied to the spanner is considered to be effort.
Before the nut can be opened, the effort must overcome the load.
Since moment is the product of a force and the perpendicular distance, the spanner with a long handle will produce a higher moment.
Therefore, a spanner with a long handle will be preferred.
Answer:
a = 7.75 [m/²]
Explanation:
To solve this problem we must use the following equation of kinematics.
where:
x = final distance = 190 [m]
Xo = initial distance = 0
Vo = initial velocity = 0 (car starts from the rest)
a = acceleration [m/s²]
t = time = 7 [s]
190 = 0 + (0*7) + 0.5*a*(7²)
190 = 0.5*49*a
a = 7.75 [m/²]
Answer:
: Rocket weight on earth
: Rocket weight on moon
Explanation:
Conceptual analysis
Weight is the force with which a body is attracted due to the action of gravity and is calculated using the following formula:
W = m × g Formula (1)
W: weight
m: mass
g: acceleration due to gravity
The mass of a body on the moon is equal to the mass of a body on the earth
The acceleration due to gravity on a body is different on the moon and on the earth
Equivalences
1 slug = 14.59 kg
Known data
Problem development
To calculate the weight of the rocket on the moon and on earth we replace the data in formula (1):
: Rocket weight on earth
: Rocket weight on moon
