warehouse/content/physics/forces-test/forces-answer-key.md

title, date, draft

title	date	draft
Forces Sample Test Answer Key	2024-09-29	true

[!faq]- Answer 1 ||\vec{F}_N||=9.8*10.0=98\mathrm{N}, so 0\le||\vec{F}_{fr}||\le\mu_s*98, where \mu_s*98=0.4*98=39.2\mathrm{N}
A) static friction, \mu_s=0
B) static friction, \mu_s=10N
C) static friction, $20$N is still not sufficient to move the box
D) static friction, $38$N is still not sufficient to move the box, but just barley
E) kinetic friction, 40\mathrm{N}>39.2\mathrm{N}, ||\vec{F}_{fr}||=0.30*98\mathrm{N}=29.4\mathrm{N}. 40\mathrm{N}-29.4\mathrm{N}=10.6\mathrm{N}, to see how fast the box will move: \frac{||\vec{F}_f||}{10.0\mathrm{kg}}=1.06 m/s. In freedom units: 2.371152 Miles an hour.

[!faq]- Answer 2 \vec{F}_A=\langle 58, 33.5 \rangle in Newtons as a force vector

[!faq]- Answer 3 F_x: $28.7$4 N
F_y: $11.6$1 N
F_{grav}: 24.5 N
F_{norm}: 12.89 N
F_{net}: 29 N, right
a: 11 \mathrm{m}/\mathrm{s}^2, right (rounded from 11.497 \mathrm{m}/\mathrm{s}^2)

[!faq]- Answer 4 10.6 N

[!faq]- Answer 5
A) 942 N, B) 846 N

[!faq]- Answer 6 (Part 1)
3.3206 ms

[!faq]- Answer 7 (Part 2)
mass of the door: 61.2244897959 kg, using the momentum equation: p_1=p_2=1*v(3.3206\mathrm{ms)=61.2244897959*v}), and you need to solve for v=?. v=0.491874746929 \mathrm{m}/\mathrm{s}

[!faq]- Answer 8 (Part 3)
T=25.547907659, time to hit wall: \approx\tfrac{T}{2}=12.7739538295 seconds.

[!faq]- Answer 9 5 N

[!faq]- Answer 10 k = 5000 N/m

[!faq]- Answer 11 970 \tfrac{\text{kg}}{\text{m}^3}

[!faq]- Answer 12 \eta=2.18 (\eta is usually treated as a dimensionless number).

[!faq]- Answer 13 1350 N/m