Question

A speed boat moving at a velocity of 25 m/s runs out of gas and drifts to a stop 3 minutes later 100 meters away. What is its rate of deceleration?

Answer 1

`0.139 m/s^2`

Explanation:

From Newton's Equations of Motion, we have:

`v=u+at`

where,
`v` is the final velocity of the boat,
`u` is the initial velocity of the boat,
`a` is the acceleration of the boat,
`t` is the time taken by the boat to accelerate/decelerate from `u` to `v`.

Since the boat decelerates from `25 m/s` to a stop (which is `0 m/s`) in 3 minutes (`=3*60=180` seconds, since all units must be from the SI system),

`u=25 m/s`

`v=0 m/s`

`t=180 s`

Substituting these values in the above equation, we have:

`0=25+a*180`

`-25=a*180`

`a=-25/180=-0.139 m/s^2`

The negative sign indicates that the boat has decelerated. We can simply write that deceleration is equal to `0.139 m/s^2`