<span>A mountain is a type of constructive force. This is because the mountains are formed (or "constructed") through the convergence of land plates. When the two (or more) plates come together, they cause the land at the fault line to shift upward, leading to the formation of mountains.</span>
Answer:
a. If an object's speed is constant, then its acceleration must be zero.
FALSE
As we know that acceleration is defined as the rate of change in velocity
![a = \frac{d\vec v}{dt}](https://tex.z-dn.net/?f=a%20%3D%20%5Cfrac%7Bd%5Cvec%20v%7D%7Bdt%7D)
so we can not say anything about the acceleration when speed is given to as and no information is given about velocity
b. If an object's acceleration is zero, then its speed must be constant.
TRUE
As we know that acceleration is defined as the rate of change in velocity
![a = \frac{d\vec v}{dt}](https://tex.z-dn.net/?f=a%20%3D%20%5Cfrac%7Bd%5Cvec%20v%7D%7Bdt%7D)
Since we know that if acceleration is 0 then velocity must be constant and hence speed is also constant
c. If an object's velocity is constant, then its speed must be constant.
TRUE
Since velocity is constant then it shows that its magnitude and direction both are constant so its speed is also constant.
d. If an object's acceleration is zero, its velocity must be constant.
TRUE
As we know that acceleration is defined as the rate of change in velocity
![a = \frac{d\vec v}{dt}](https://tex.z-dn.net/?f=a%20%3D%20%5Cfrac%7Bd%5Cvec%20v%7D%7Bdt%7D)
Since we know that if acceleration is 0 then velocity must be constant
e. If an object's speed is constant, then its velocity must be constant.
FALSE
Speed is just the magnitude so we can not say about its direction and hence if speed is constant then velocity may or may not change
Answer:
t = 2.2 s
Explanation:
Given that,
A person observes a firework display for A safe distance of 0.750 km.
d = 750 m
The speed of sound in air, v = 340 m/s
We need to find the between the person see and hear a firework explosion. let it is t. So, using the formula of speed.
![v=\dfrac{d}{t}\\\\t=\dfrac{d}{v}\\\\t=\dfrac{750\ m}{340\ m/s}\\\\t=2.2\ s](https://tex.z-dn.net/?f=v%3D%5Cdfrac%7Bd%7D%7Bt%7D%5C%5C%5C%5Ct%3D%5Cdfrac%7Bd%7D%7Bv%7D%5C%5C%5C%5Ct%3D%5Cdfrac%7B750%5C%20m%7D%7B340%5C%20m%2Fs%7D%5C%5C%5C%5Ct%3D2.2%5C%20s)
So, the required time is 2.2 seconds.