Answer:
A. velocity has a direction .. .
with magnitude too but speed has only magnitude
Answer:
ok
Explanation:
The Earth is made of several subsystems or "spheres" that interact to form a complex and continuously changing whole called the Earth system. Scale
Processes operating in the Earth system take place on spatial scales varying from fractions of millimeters to thousands of kilometers, and on time scales that range from milliseconds to billions of years.
Examples of instantaneous - breathing; rotation of the Earth; earthquake
Examples of long term - making coal; plate tectonics
Cycles
The Earth system is characterized by numerous overlapping cycles in which matter is recycled over and over again. Cycles involve multiple spheres and systems interactions.
Examples of cycles: day and night; rock cycle; seasons
Energy
The Earth system is powered by energy from two major sources: the Sun and the planet's internal heat.
Humans and the Earth System
People are part of the Earth system and they impact and are impacted by its materials and processes.
Answer:
Second Trial satisfy principle of conservation of momentum
Explanation:
Given mass of ball A and ball B 
Let mass of ball
and
Final velocity of ball 
Final velocity of ball 
initial velocity of ball 
Initial velocity of ball 
Momentum after collision 
Momentum before collision 
Conservation of momentum in a closed system states that, moment before collision should be equal to moment after collision.
Now, 
Plugging each trial in this equation we get,
First Trial

momentum before collision
moment after collision
Second Trial

moment before collision
moment after collision
Third Trial

momentum before collision
moment after collision
Fourth Trial

momentum before collision
moment after collision
We can see only Trial- 2 shows the conservation of momentum in a closed system.
Answer:
The velocity of the truck after this elastic collision is 15.7 m/s
Explanation:
It is given that,
Mass of the car, 
Mass of the truck, 
Initial velocity of the car,
Initial velocity of the truck, u₂ = 0
After the collision the velocity of the car is, v₁ = -11 m/s
Let v₂ is the velocity of the truck after this elastic collision. Using the conservation of momentum as :

So, the velocity of the truck after this elastic collision is 15.7 m/s. Hence, the correct option is (c).
Answer:
Impulse will be 12 kgm/sec
So option (b) will be correct option
Explanation:
We have given mass of the baseball m = 0.15 kg
Ball speed before hit 
Ball speed after hitting
( negative direction due to opposite direction )
We have to find the impulse
We know that impulse is equal; to the change in momentum
So change in momentum = 
So option (b) will be correct option