Question a-phys

2.1 Nonlinear Functions - Quadratic graphs and vertex form
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A physics class is planning an experiment about a toy rocket. The equation y=-16x-5.62+502 gives the estimated height y , in feet, of the toy rocket x seconds after it is launched into the air. Which of the following is the best interpretation of the vertex of the graph of the equation in the xy-plane?

A.

This toy rocket reaches an estimated maximum height of 502 feet 16 seconds after it is launched into the air.

B.

This toy rocket reaches an estimated maximum height of 502 feet 5.6 seconds after it is launched into the air.

C.

This toy rocket reaches an estimated maximum height of 16 feet 502 seconds after it is launched into the air.

D.

This toy rocket reaches an estimated maximum height of 5.6 feet 502 seconds after it is launched into the air.

A physics class is planning an experiment about a toy rocket. The equation y = -

Hard-difficulty · SAT Math · Nonlinear Functions — Quadratic graphs and vertex form. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice B is correct. The vertex of the graph of a quadratic equation is where it reaches its minimum or maximum value. When a quadratic equation is written in the form y=a(x-h)2+k, the vertex of the parabola represented by the equation is (x,y)=(h,k). In the given equation y=-16(x-5.6)2+502, the value of h is 5.6 and the value of k is 502 . It follows that the vertex of the graph of this equation in the xy-plane is (x,y)=(5.6,502). Additionally, since a = - 16 in the given equation, the graph of the quadratic equation opens down, and the vertex represents a maximum. It’s given that the value of y represents the estimated height, in feet, of the toy rocket x seconds after it is launched into the air. Therefore, this toy rocket reaches an estimated maximum height of 502 feet 5.6 seconds after it is launched into the air.

Choice A is incorrect. The 16 in the equation is an indior of how narrow the graph of the equation is rather than where it reaches its maximum.

Choice C is incorrect. The 16 in the equation is an indior of how narrow the graph of the equation is rather than where it reaches its maximum.

Choice D is incorrect. This is an interpretation of the vertex of the graph of the equation y=-16(x-502)2+5.6, not of the equation y=-16(x-5.6)2+502.