(6) a) A bullet with mass=30 g is fired from a rifle with a velocity of v1=400m/
ID: 1491116 • Letter: #
Question
(6)
a) A bullet with mass=30 g is fired from a rifle with a velocity of v1=400m/s. It passes through a window pane d=2 mm thick and its velocity is reduced to v2=200m/s. Calculate the average force F applied to the bullet by the pane.
b) Write and comment the Newton's law of universal gravitation. Apply this law in the case below: A sphere of 40kg is attracted by another sphere of 15 kg with a force equivalent with the weight of an object with mass m=0.1 mg. Find the value fo the universal constant G of gravitation if the centers of sphere are 20 cm apart.
c) Using the numerical values below, calculate the gravitational acceleration g for objects near the surface of the Earth. Find also the value of this gravitational acceleration for objects near he surface of the Moon. If your mass is 70 kg, what would you weigh on the Moon? (G=6.67*10-11 Nm2/kg2 ; ME=5.98*1024 kg ; RE=6.4*106 m ; MM=7.36*1022 kg ; RM = 1.74*106 m)
Explanation / Answer
a)
F = m(V^2-u^2/2d) = 30*10^-3*(400^2-200^2)/2*2*10^-3 = 9*10^5 N
b)
F =Gm1m2/r^2
G = F*r^2/m1*m2
G = 0.1*10^-6*9.8*0.2^2/40*15 = 6.53*10^-11 Nm2/Kg2
c)
g = GM/R^2 = 9.8 m/s2
d)
g on Moon = GMass of Moon/Rm^2 = 1.62 m/s2
W = 70*1.62 = 113.4 N
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