- #1
AgentRedfield
- 10
- 0
Homework Statement
A small car of mass m is released at height h on a steel track. The car rolls down the track and through a loop of radius R. At the end of the track, the car rolls off the track, which is positioned at a height H above the floor. Neglect friction and the small amount of rotational motion of the wheels of the car. Solve in terms of h, m, R, H, and g.
(a) Find the velocity of the car at point B (bottom of the loop).
(b) Find the velocity of the car at point C (top of the loop).
(c) Determine the height h at point A such that the car just barely makes contact with the loop at point C as it goes through the loop.
(d)When the car is moving at minimum speed, what provides the centripetal force on the car:
i. at point B?
ii. at point C?
iii. at point D (side of the loop)?
(e) Determine the distance from the end of the track that the car will land on the floor.
Homework Equations
##mgh + \frac{1}{2}mv^2##
##a=\frac{v^2}{2}##
##F_net=\frac{mv^2}{2}##
##F_N \pm F_g = F_C##
##x=x_o +v_o t +\frac{1}{2}at^2##
The Attempt at a Solution
(a) I think I understood this, I used the first equation above and got: [itex]v=\sqrt{2gh}[/itex]
(b) I started to solve this as follows: ##F_N + mg = \frac{mv^2}{2}##
The problem is that when solving for v I can't figure out what to substitute for the normal force. My intermediary answer is [itex]v=\sqrt{\frac{(F_N + mg)R}{m}}[/itex]
(c) The height at point C = 2R. I used [itex]mgh + \frac{1}{2}mv^2 = constant[/itex] which I think would make the answer be h = 2R.
(d)
i. I think it would be -mg because that's the only downward force.
ii. I'm having the same trouble with this as I am with part b. The normal force combined with the force of gravity is making my substitutions became circular.
iii. The normal force equals the centripetal force so I believe it would be [itex]\frac{2mgh}{R}[/itex]
(e)
[itex]x=x_o +v_o t +\frac{1}{2}at^2[/itex] and [itex]t=\sqrt{\frac{2H}{g}}[/itex] so the answer would be [itex]x=\sqrt{2gh}\sqrt{\frac{2H}{g}}[/itex]
4. Conclusion
Parts b, c, & d have me the most confused so any help with understanding them would be very appreciated. Problems that require the use of only certain variables such as this one have given me the most trouble in physics so any tips or tricks you have when approaching them would be awesome as well. Thank you very much for your time.