Question

A parachute slows a skydiver from 85 m/s

to 45 m/s in 4.5 seconds? What is the
acceleration of the parachute?
A. 8.9 m/s2
B. -8.9 m/s
2
C. 0.1 m/s2
D. -0.1 m/s
2

Answer 1

`\boxed {\boxed {\sf B. \ -8.9 \ m/s^2}}`

Step-by-step explanation:

Acceleration is found by dividing the change in velocity by the change in time.

`a=\frac {v_f-v_i}{t}`

The parachute slows from 85 m/s to 45 m/s. Therefore, the final velocity is 45 meters per second and the initial velocity is 85 meters per second. The time is 4.5 seconds.

`v_f= 45 \ m/s \\v_i= 85 \ m/s \\t= 4.5 \ s`

Substitute the values into the formula.

`a= \frac {45 \ m/s- 85 \ m/s}{4.5 \ s}`

Solve the numerator and subtract.

`a= \frac {-40 \ m/s}{4.5 \ s}`

Divide.

`a=-8.888888889 \ m/s/s`

If we round this to the nearest tenth, the 8 in the hundredth place tells us to round the 8 up to a 9.

`a \approx -8.9 \ m/s/s= -8.9 \ m/s^2`

The acceleration of the parachute is approximately -8.9 meters per square second. The value is negative because the parachute is slowing down.