# physics mindbender?

Discussion in 'MCAT Discussions' started by gabdolce, Jun 10, 2012.

1. SDN is made possible through member donations, sponsorships, and our volunteers. Learn about SDN's nonprofit mission.
1. ### gabdolce 5+ Year Member

55
2
Aug 8, 2011
So you are in a car going 60 mph an hour on the highway. In front of it a ways [10 m], there is a van with a ramp [at 30 degrees from the horizontal] on the back going at 55 mph in the same direction.

Once the car reaches the van [slowly], does the car begin to accelerate incredibly quickly?

How do you calculate the relative velocities once the car reaches/is first completely on the ramp? The relatively velocity of the car is 5 mph [60-55mph]. But once it is on the ramp, are you looking at a relative velocity of 60mph-0mph?

242
2
May 14, 2012

4. ### Jamie561 5+ Year Member

497
53
Sep 2, 2011
Protip: you are using two different frames of reference.

5. ### MedicalAuthorClass of Twenty Seventeen 5+ Year Member

508
2
Apr 18, 2011
Sounds like its the same as suspending a car in mid-air, getting the wheels rolling up to 60 miles an hour, and dropping it.

Most likely the tires will start to skid and gradually gain traction based on the maximum force friction can push forward the car.

Cus if the ramp is frictionless, that cars going nowhere!

---
I am here: http://tapatalk.com/map.php?doeyo5

6. ### MedicalAuthorClass of Twenty Seventeen 5+ Year Member

508
2
Apr 18, 2011
Correction, it will go up the ramp if it's frictionless, but at 5mph and slowing down. Just my point was to show that a certain amount of friction is needed to accelerate the car up the ramp, so the car will have a max acceleration it can achieve, and the extra turning of the wheels will just lend to skidding.

---
I am here: http://tapatalk.com/map.php?w4a0qk