Answer:
1. True
2. True
3. False
4. False
5. True
6. False
Explanation:
Acceleration: It refers to the change in velocity/speed of an object with respect to time. When the speed increases with time we call it acceleration and when its decreases it is called as deceleration. Let us analyze each instance individually:
1. When roller coaster starts to roll down the track its speed will increase with time. That means it is accelerating.
2. When the ball reaches at the peak of its trajectory, it comes to a stop for a fraction of a second that means it decelerates.
3. Since the velocity remains constant there is no acceleration.
4. Since the speed is no changing with time, there is no acceleration.
5. Since the moving plane comes to a stop, it is a case of deceleration.
6. Since the truck is moving at a constant speed so the acceleration is zero.
Answer:

Explanation:
As we know that the acceleration due to gravity decreases with height.
At certain height it will get to the half of its value on the surface of the earth.
As we know that the weight on the surface of the earth is given as:

where:
m = mass of the object
g = acceleration due to gravity of the substance
Since mass of the substance is constant so the variation is weight is possible only due to change in the acceleration due to gravity.
<u>We know that the variation of the acceleration due gravity with height is given as:</u>

where:
value to acceleration due to gravity at height h
g = acceleration due to gravity at the earth's surface
h = height of the object
R = radius of the earth = 
according to question the weight becomes half, so,:

is the height a rocket has to go above Earth's surface before its weight is half of what it is on Earth.
Answer:
76 m /s
Explanation:
maximum height, H = 19.7 m
Angle of projection, θ = 15 degree
Let u be the projectile launch speed
Use the formula of maximum height


u = 75.9199 = 76 m /s
Answer:
Hz
Explanation:
In alternating current (AC) circuits, voltage (V) oscillates in a sine wave pattern and has a general equation as a function of time (t) as follows;
V(t) = V sin (ωt + Ф) -----------------(i)
Where;
V = amplitude value of the voltage
ω = angular frequency = 2 π f [f = cyclic frequency or simply, frequency]
Ф = phase difference between voltage and current.
<u><em>Now,</em></u>
From the question,
V(t) = 230 sin (100t) ---------------(ii)
<em><u>By comparing equations (i) and (ii) the following holds;</u></em>
V = 230
ω = 100
Ф = 0
<em><u>But;</u></em>
ω = 2 π f = 100
2 π f = 100 [divide both sides by 2]
π f = 50
f =
Hz
Therefore, the frequency of the voltage is
Hz