Question

A car initially moving at 32 m/s slows to a stop in 15 seconds. What is the car's average

acceleration?
A)0.47 m/s2
B) 480 m/s2
C) 17 m/s2
D) none of these
E) 2.1 m/s2

Answer 1

Either D.) or E.). See explanation.

Step-by-step explanation:

Use kinematic equation #1,
`v_f=v_i+at` and rewrite to solve for acceleration:
`a=(v_f-v_i)/(t)`. For this problem, let

`v_f=0.0(m)/(s)\\v_i=32.0(m)/(s)\\t=15.0s`

So,

`a=(0.0(m)/(s)-32.0(m)/(s))/(15.0s)\\a=(-32.0(m)/(s))/(15.0s)\\a=-2.13(m)/(s^2)`

This answer doesn't appear in the choices given. In the physics classes I've taken, the correct answer would be D.). But if your instructor wants the magnitude of the acceleration, then E.) is the correct answer. The fact that none of the answers are negative for a deceleration problem is a bit confusing to me.

Answer 2

E

Step-by-step explanation: