A proton (m= 1.67x10^-27kg) moving at 4.0x10^7m/s shoots through a sheet of foam plastic .25 cm thick and emerges with a speed of 1.5x10^7 m/s A) How long does it take to pass through the plastic?B) What average force retards the proton's motion through the plastic?Hints: Fext T+MVi=MVf Ans: A. 9.09x10^-11s B.4.59x10^-10N
Ans: A. 9.09x10^-11s B.4.59x10^-10N
A) d = Vavg * t 0.0025 m = ?(4.0 + 1.5)e7m/s * t t = 9.09e-11 s B) The hint uses the impulse equation: impulse + initial p = final p F * 9.09e-11s + 1.67e-27kg * 4.0e7m/s = 1.67e-27kg * 1.5e7m/s F = -4.59e-10 N Since the force is against the direction of motion, I think it should have a negative sign; your answer suggests it isn't warranted. Without the hint, you could do acceleration a = Δv / Δt = (1.5 - 4)e7 m/s / 9.09e-11s = -2.75e17 m/s? and then F = m*a = 1.67e-27kg * -2.75e17m/s? = -4.59e-10 N If you find this helpful, please award Best Answer!
