1) A 10,000 kg freight car is rolling along a track at 3.00 m/s. Calculate the t

ID: 1607975 • Letter: 1

Question

1) A 10,000 kg freight car is rolling along a track at 3.00 m/s. Calculate the time needed for a force of 1000 N to stop the car.

2) A car moving at 10 m/s (36 mph) crashes into a barrier and stops in .25 m.

a. What is the time required to stop the car?

b. If a 20 kg child were to be stopped in the same time as the car, what average force must be exerted?

c. Approximately what is the mass of an object whose weight equals the force from the previous question? Could this mass be lifted with an arm?

a = F/m = - 1000/10000 = - 0.10 m/s^2

Applying v = u + a t

0 = 3 - 0.1t

t = 30 sec

2.(a) vf^2 - vi^2 =2 a d

0^2 - 10^2 = 2(a)(0.25)

a = - 200 m/s^2

vf = vi + a t

0 = 10 - 200t

t = 0.05 sec

(b) F = m a = 20 x 200 = 4000 N

no, it can not be lifted.

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.