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# energy and momentum watch

1. i nid help in solving these problems.

4. A satellite of mass of 500kg is at a position 100km above the earth (G=6.67x1024Nm2/kg2 me=5.98x1024 kg and re=6.37x106 m). If the period of the satellite is 86.3min, calculate
c) the energy needed to escape from the 100km altitude.
d) the energy needed to move the satellite to an altitude of 200km.

5. A cart with a mass of 500g and a spring bumper (K=500N/m) traveling with a velocity of 4m/s collides with another cart with a mass of 300g at rest. Assuming the collision is elastic determine
c) the maximum elastic potential energy store in the spring
d) the minimum separation if the length of the spring bumper is 30cm.

7. Two students of mass 60kg each standing on a cart with a mass of 40kg jump off the cart with a velocity of 6m/s relative to the cart. Assuming no friction calculate the velocity of the cart after both students have jumped off the cart.
2. (Original post by jeongsuman)
7. Two students of mass 60kg each standing on a cart with a mass of 40kg jump off the cart with a velocity of 6m/s relative to the cart. Assuming no friction calculate the velocity of the cart after both students have jumped off the cart.
I don't think the answer is 5.85m/s.

The mass of the two students will be 120 Kg their momentum will be 120*6=720Ns

The momentum of the cart will be equal and opposite.
40v =720
v=720/40 = 18m/s

What number is the question?
3. (Original post by jeongsuman)
(G=6.67x1024Nm2/kg2 me=5.98x1024 kg and re=6.37x106 m)
Forgive me if I am wrong but isnt G the universal gravitational constant 6.67x10-11Nm²kg-2
4. (Original post by jeongsuman)
i nid help in solving these problems.

7. Two students of mass 60kg each standing on a cart with a mass of 40kg jump off the cart with a velocity of 6m/s relative to the cart. Assuming no friction calculate the velocity of the cart after both students have jumped off the cart.
Model the boys as 1 particle of m=120kg v=6/s
I=m(v-u)
I=120(6-0)
I=720Ns

For the cart:
I=40v
720=40v
v=18m/s

Since theres no initial momentum its just the same then yours. I am not going to pretend to be a mechanics expert though, so might not be right it does seem abit to easy though.

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