1.) A 7159 N piano is to be pushed up a(n) 2.26 m
frictionless plank that makes an angle of 25.6 degrees with the horizontal.
Calculate the work done in sliding the piano
up the plank at a slow constant rate.
Answer in units of J.
2.) A 20 g bullet is accelerated in a rifle barrel
45 cm long to a speed of 354 m/s.
Use the work-energy theorem to find the
average force exerted on the bullet while it is
being accelerated.
Answer in units of N.
3.) A 4.17 g bullet moving at 506.1 m/s penetrates
a tree trunk to a depth of 4.64 cm.
Use work and energy considerations to
find the magnitude of the force that stops the
bullet.
Answer in units of N.
posted these already but the answers were marked incorrect
3 answers
1. To answer this you use the formula W=fd, you have the force because the piano is moving at a slow constant rate so its overcoming its gravity in the X direction, so you can find F and 2.26M is your Displacement (D)
i don't know how to do than the last person who answered tried it but it involved sin and calculus stuff like that
1. M*g = 7159 N.
M = 7159/g = 7159/9.8 = 731 kg.
Fp = 7159*sin25.6 = 3093 N. = Force parallel to the plank.
Fap-Fp = M*a.
Fap - 3093 = M*0 = 0.
Fap = 3093 N. = Force applied.
Work = Fap*d = 3093 * 2.26 = 6991 J.
2. Work = KE2-KE1 = 0.5M*V^2- 0 = 0.5*0.02*354^2 = 1253 J.
M = 7159/g = 7159/9.8 = 731 kg.
Fp = 7159*sin25.6 = 3093 N. = Force parallel to the plank.
Fap-Fp = M*a.
Fap - 3093 = M*0 = 0.
Fap = 3093 N. = Force applied.
Work = Fap*d = 3093 * 2.26 = 6991 J.
2. Work = KE2-KE1 = 0.5M*V^2- 0 = 0.5*0.02*354^2 = 1253 J.
1 answer