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Topic: Very difficult physics problem? i think its unsolvable?**Question:**
please help me
A(n) 16 g object moving to the right at
30 cm/s overtakes and collides elastically with
a 32 g object moving in the same direction at
14 cm/s. Find the velocity of the slower object after
the collision.
Answer in units of cm/s.

June 26, 2019 / By Anitra

This is a rather lengthy problem, but certainly solvable. Here is an outline; Since its an elastic collision both kinetic energy & momentum must be conserved; m1v1 + m2v2 = m1u1 + m2u2 m1v1^2 + m2v2^2 = m1u1^2 + m2u2^2 (the 1/2 cancels) Here it is a good idea to use the given that m2 = 2m1 v1 + 2v2 = u1 + 2u2 v1^2 + 2v2^2 = u1^2 + 2u2^2 Generally I like to solve a problem algebraically before putting in numbers, but this problem is worth putting in the numbers first; Given; v1=30 & v2=14. Sub these values in; 58 = u1 + 2u2 1292 = u1^2 + 2u2^2 Solve for u1 in the 1st eq. then square it and sub in the 2nd eq; 1292 = 3364 - 232u2 + 4u2^2 + 2u2^2 6u2^2 - 232u2 + 2072 = 0 Now use the quadratic eq. to find u2. There will be two solutions and you must use each solution to get two solutions for u1. Then you have to look at the two pair of solutions and reject the solutions that are not possible. For example, u1 can't be positive at the same time u2 is negative as that would imply one went thru the other. Also u1 can't be greater then u2 ,for the same reason. You might want to check my math above. I could've made an error. But that's the procrdure.

👍 170 | 👎 1

Did you like the answer? The maximum decelerating force on the car is a = gKk where g is gravity (9.8 m/s²) and Kk is the coefficient of kinetic friction. The velocity of an object after decelerating x meters with deceleration a and initial velocity V0 is V² = V0²-2ax. Since V will be 0 when the car stops x = V0²/(2a) and now it's just plug 'n play. You do the arithmetic ☺ HTH Doug

There are several steps to this problem. First you need to find the acceleration of the car on both the wet and dry road. Remember that F(friction)=-C*F(normal), where C is the coefficient of friction. Once you have a, you can use v-vo=at to find the time it take the car to stop. Finally use x-x0=1/2at^2+vot to find the distance traveled.

those of you who're suggesting that the preliminary speed is going to be better than the staggering speed are incorrect. The ball is being thrown from 2.40 5 meters intense by potential of the time the ball hits the floor it ought to have traveled added and persevered to enhance up so its very final speed is going to be better than its preliminary speed. the velocities would be equivalent while the ball is coming down and is at 2.40 5 meters even though it stll has 2.40 5 meters beforehand it hits the floor. Does that make sense? The preliminary speed is 9.seventy 8 m/s^2

👍 70 | 👎 -6

In a perfectly elastic collision, kinetic energy is conserved. Use this to set up a pair of simultaneous equations for the situation and solve. If you know about coefficient of elasticity (= 1 for a perfectly elastic collision), you can solve it faster.

👍 70 | 👎 -13

Taking Physics C is a good idea especially if you are going to be a physics major. I'm actually taking the class right now, and it's one of the hardest classes at high school! I'm also taking Calc BC at the same time, and compared to physics, calc is a breeze. Physics C actually has very little calculus. Most of it is simple arithmetic. However, knowing how to derive and intergrate might help out a bit. Your knowlege of calc can be very limited, and you will still be able to do ok in the class. I'm sure you won't end up failing the class. Physics is a difficult class in general. Typically, everyone fails the quizzes and the tests, but we have a generous teacher who curves our grades and gives us plenty of extra credit. If you're going to enroll in the class, just be ready to fail the tests. I've made a D and a couple of C's on the quizzes, and I'm still standing. And I just recently failed a test today! =D I've heard that the AP test is difficult if you're taking Mechanics and E&M. Just mechanics alone isn't bad. I took the Physics B test last year, and I understood only half (or even less than half) of the material, and I still made a 4. I've heard that you only need a 50% on the AP exam to make a 5. There's actually no real way you can study for the AP exam. You can buy a Princeton Review book if those help you. I barely studied because I had other tests going on at the time, and I was drained by the time the test came around. You'll be fine though! Don't worry! =)

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