A and B are equivalent. That's one way instruments are often grouped. (the "sopranos", the "altos", the "bass")
C is another way instruments are often grouped; (the "woods", the "brass")
D is another way instruments are often grouped; (the "strings", the "percussions")
Answer:
-
Explanation:
We are given that
Mass of cars= m=1900 kg
Initial speed of car=u=20 m/s
Final speed of car=v=0
Time=
=1.3 s
We have to find the average force exerted on the car.
Average force=



Hence, the average force exerted on the car that hits a line of water barrels=-
Answer:
a) 
b) 
c) 
Explanation:
From the exercise we know the initial velocity of the projectile and its initial height

To find what time does it take to reach maximum height we need to find how high will it go
b) We can calculate its initial height using the following formula
Knowing that its velocity is zero at its maximum height



So, the projectile goes 1024 ft high
a) From the equation of height we calculate how long does it take to reach maximum point



Solving the quadratic equation



So, the projectile reach maximum point at t=2s
c) We can calculate the final velocity by using the following formula:


Since the projectile is going down the velocity at the instant it reaches the ground is:

Kinetic energy = (1/2) (mass) (speed)²
The rock's kinetic energy is not
(1/2) (4 kg) (10 m/s)²
= (1/2) (4 kg) (100 m²/s²)
= 200 Joules .
It may be more, or it may be less. The only thing
we can be sure of is that it is not 200 Joules.