SAT Subject Physics Practice Question 177: Answer and Explanation

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Question: 177

23.

Two cannons shoot cannonballs simultaneously. The cannon embedded in the ground shoots a cannonball whose mass is half that of the cannonball shot by the elevated cannon. Also, the initial speed of the cannonball projected from ground level is half the initial speed of the cannonball shot horizontally from the elevated position. Air resistance is negligible and can be ignored. Each cannonball is in motion for more than 2 seconds before striking the level ground.

Let a1 denote the acceleration of the cannonball of mass m one second after launch, and let a2 denote the acceleration of the cannonball of mass m/2 one second after launch. Which of the following statements is true?

A.

(A)a1= 4a2
B.

(B)a1= 2a2
C.

(C)a1= a2
D.

(D)a2= 2a1
E.

(E)a2= 4a1

Correct Answer: C

Explanation:

While the cannonballs are in flight, the only force they feel is the gravitational force, so the acceleration of each cannonball is equal to g.

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