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Author:
-JAMES- Posts: 12,314
7/17/18 6:41 P

F = M a ( Force = mass times acceleration)

The mass is 1900 kilograms.

Acceleration is the rate of change of velocity. So acceleration times the time of during which that is happening is the change in velocity:
v2 - v1 = change in velocity = 0 - 12 (m/sec) = -12 m/sec
For a vehicle to go from 12 (m/sec) to zero in 3.1 seconds the change in velocity is:
v2 - v1 = at

where t is 3.1 seconds

v2 - v1 is -12, and t is 3.1, so the accelation is -3.87 m/(sec*sec)

F = M a = 1900 * (-3.87 ) Newtons = - 7353 Newtons

They are asking for the magnitude of the force (so they don't care about direction or sign, so you might as well just drop that negative sign).

Feel free to spark mail me any physics questions. (I am a Dr. of Physics)
- James

Edited by: -JAMES- at: 7/17/2018 (21:21)
James

All time highest weight : 217 pounds

Starting weight : 195.0 pounds (June 7, 2012)
Final weight : 168.2 pounds (July 23, 2013)

current weight: 178.5
217
201.5
186
170.5
155
ELPELOS Posts: 992
7/17/18 4:45 P

d. 7,400 N

Body Fat %: 9.5
16
13.5
11
8.5
6
SHERYLDS Posts: 17,770
7/17/18 12:06 P

Force Formula
www.softschools.com/formulas/physics/force
_formula/2/

Sheryl, New Jersey EST, SUMMER 5% Challenge-KITCHEN CHAMPIONS

Pounds lost: 5.0
0
3
6
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12
VICTORIA725 Posts: 21
7/17/18 8:50 A

A 1,900kg truck has an initial speed of 12 m/s. The driver applies the brakes, and the truck stops in 3.1 s.
What is the best estimate of the magnitude of the average braking force of the truck?

a. 23,000 N
b. 490 N
c. 71,000 N
d. 7,400 N

current weight: 258.0
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