Definitely D. The brakes on a bike rub against the wheel. Not sure about the others.
Answer:
Maximum height reached by the rocket is

total time of the motion of rocket is given as

Explanation:
Initial speed of the rocket is given as

acceleration of the rocket is given as

engine stops at height h = 150 m
so the final speed of the rocket at this height is given as



so maximum height reached by the rocket is given as the height where its final speed becomes zero
so we will have



Now the total time of the motion of rocket is given as
1) time to reach the height of 150 m



2) time to reach ground from this height



so total time of the motion of rocket is given as

A billiard ball collides with a stationary identical billiard ball to make it move. If the collision is perfectly elastic, the first ball comes to rest after collision.
<h3>Why does the first ball comes to rest after collision ?</h3>
Let m be the mass of the two identical balls.
u1 = velocity before the collision of ball 1
u2 = 0 = velocity of second ball that is at rest
v1 and v2 are the velocities of the balls after the collision.
From the conservation of momentum,
∴ mu1 + mu2 = mv1 + mv2
∴ mu1 = mv1 + mv2
∴ u1 = v1 + v2
In an elastic collision, the kinetic energy of the system before and after collision remains same.

∴ 
∴ 
∴
₁
₂ = 0
- It is impossible for the mass to be zero.
- Because the second ball moves, velocity v2 cannot be zero.
- As a result, the velocity of the first ball, v1, is zero, indicating that it comes to rest after collision.
<h3>What is collision ?</h3>
An elastic collision is a collision between two bodies in which the total kinetic energy of the two bodies remains constant. There is no net transfer of kinetic energy into other forms such as heat, noise, or potential energy in an ideal, fully elastic collision.
Can learn more about elastic collision from brainly.com/question/12644900
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Answer:
A - elastic since many other fast food items could be considered close substitutes.
Explanation:
The price elasticity of demand is how much the demand of the Big Macs will change due to a 1% change in price. Should the elasticity be greater than 1, the Big Macs will be elastic. Should it be less than 1, the Big Macs are inelastic.
Demand elasticity is calculated as the percentage change in quantity demanded divided by a percentage change in price.
Since Big Macs are (i) a luxury good, and (ii) have close substitutes (other burgers available at McDonalds and other fast food stores), we will say their elasticity is greater than 1.
This means that the demand of Big Macs will change due to a 1% increase in price due to the presence of close substitutes.