Answer:
The acceleration of the train is 5 m/s².
Explanation:
Given:
let the initial velocity of a train = 5 m/s and
final velocity of a train = 45 m/s
time taken = 8 s
To find:
acceleration: ?
Solution:
We define acceleration as change in velocity per unit time that is the difference between the final velocity and initial velocity divided by time.

On substituting the above values we get the required acceleration

Therefore,the acceleration of the train is 5 m/s².
Answer:
E) The average velocity of the car is 90.0 miles per hour in the direction of motion.
Explanation:
Given;
distance covered by the car, d = 90 miles
time taken, t = 60 minutes = 1 hour
The average velocity of the car is given by change in displacement per change in time;
V = Δd / Δt

Therefore, the average velocity of the car is 90.0 miles per hour in the direction of motion.
Answer:
See below
Explanation:
Find the NET forces on the objects
A 20==>
B 0
C 30==>
D 15==>
So biggest accel = C because it has the most force acting on it
next is A because it has the next biggest force
next is D then B ...B has no net force acting on it
Answer: Concentration of H+ =10^-7; log of 10^-7=7 so pH=7
Explanation:
Explanation:
It is given that,
Fundamental frequency, f = 220 Hz
(a) We know that at 0 degrees, the speed of sound in air is 331 m/s.
For open pipe, 
l is the length of pipe
Also,


(b) Let f' is the fundamental frequency of the pipe at 30 degrees and v' is its speed.


v' = 348.71 m/s
So, 

f' = 232.4 Hz
Hence, this is the required solution.