Answer:
The velocity of the boat with respect to the ground is 3 km/h
Explanation:
The speed of an object is different depending on the reference system you use. This is called relative speed.
A boat travels upstream, this means that it moves in the opposite direction to the river current.
A boat travels upstream, this means that it moves in the opposite direction to the river current. Then, if the boat moves in the positive direction of the x axis at 10 km / h with respect to the water of a river, the water flows in the negative direction of the x axis at 7 km / h with respect to the ground.
This causes the speed of the boat relative to the ground to be calculated as follows:
<em>VbG = Vbw - VwG
</em>
where VbG is the speed of the boat relative to the ground, Vbw is the speed of the boat relative to the water of the river and VwG is the speed of the water relative to the ground.
So: VbG=10 km/h – 7 km/h
<u><em>VbG= 3 km/h
</em></u>
The direction of this velocity is in the positive x-direction.
Answer:
beta particles
Explanation:

Given mass = 14.0 g
Molar mass = 137 g/mol

According to avogadro's law, 1 mole of every substance weighs equal to its molecular mass and contains avogadro's number
of particles.
1 mole of cesium contains atoms =
0.102 moles of cesium contains atoms =
The relation of atoms with time for radioactivbe decay is:

Where
=atoms left undecayed
= initial atoms
t = time taken for decay = 3 minutes
= half life = 30.0 years =
minutes
The fraction that decays : 
Amount of particles that decay is = 
Thus
beta particles are emitted by a 14.0-g sample of cesium-137 in three minutes.
The time spent in the air by the ball at the given momentum is 6.43 s.
The given parameters;
- <em>momentum of the ball, P = 0.9 kgm/s</em>
- <em>weight of the ball, W = 0.14 N</em>
The impulse experienced by the ball is calculated as follows;

where;
is impulse
is change in momentum
The time of motion of the ball is calculated as follows;

Thus, the time spent in the air by the ball at the given momentum is 6.43 s.
Learn more here:brainly.com/question/13468390
Because the scientific method can go around in a circle as many times as neccisary to get the results you need