Physics Work constant force?
A 1200kg car coasts on a horizontal road with a speed of 20m/s. After crossing a sandy stretch of the road 30.0m long its speed decreases to 17m/s.
(a) how much work is done on the car?
(b) find the magnitude of the average force on the car
Do you use the 1/2 mv*2 formula and subtract to find work? I'm beginning this chapter in physics and don't understand this problem fully.
Ok, so I used the 1/2mv*2 formula and got
1/2 (1200)(20*2) - 1/2 (1200)(17*2) = 66,600 J
Then used the V*2 = Vi*2 + 2(a)d and got 17*2 = 20*2 + 2a(30)
a = (-1.85)m/s*2
F = ma
F = (1200)(1.85)
F = 2220 N
positive since its magnitude? or should it be negative?