Vincezor's Physics Questions Thread

[Vincezor]

I realised I have a lot of questions regarding motion (I find it quite hard to understand ) so I decided to start up a thread for questions.

So, here goes

1. An unpowered model car of mass 0.02kg begins a loop the loop (vertical circle) of radius 25cm at ground level at a speed of 3.8m/s. Calculate the speed of the car at the top of the track and find the magnitude of the normal reaction force at the top of the track.

2. A 2kg mass is swung in a vertical circle of radius 0.60m so that it has a speed of 2.8m/s at the top of the circle. What is the size of the tension in the string at the:
a) top of the circle?
b) bottom of the circle?

3. A 70kg student rides a Ferris wheel of radius 8m. If the wheel moves at a constant speed, completing one revolution in 90 seconds, calculate the size of the force on the student provided by the seat at:
a) the top
b) the bottom
of the vertical circle travelled by the wheel.


Also, I'll try and post the solutions (or link to the relevant post) for each question if needed.

[xZero]

1) r=25cm, u=3.8ms^-1, m=0.02kg. Assuming that all friction forces are negligible, F=mv^2/r, sub the values in to find the net force. Now at the top of the track, the net force is pointing downward in the same direction as the gravity. Draw a free body diagram and place the Normal force in the right direction and work it out from there.

2) a) same thing as above
b) same thing except you draw the free body diagram at the bottom of the circle (note the direction of the tension force)

3) same concept, but the question didn't tell you the velocity so you have to find out from 1 rev per 90 second where 1 rev = circumference of the wheel.