Motion help-URGENT (1 Viewer)

[damo17]

The 'shock drop' ride raises it's passengers 4.3m into the air before dropping them. For the first part after release the passengers are in free fall before undergoing braking in the last 0.8m using a series of springs. \
When full the ride has a mass of 1500kg.Assume no losses due to friction or air resistance.

a) What is the minimum work done in raising a full ride to it's starting point.
b) What is it's kinetic energy of the ride just before braking commences.
c) hence, determine the max velocity of the ride.
d) how much elastic energy must be absorbed by the braking system.


I don't need people to show working out but what would be really helpful it to tell me what values and formulas I would use for each part. I have tried it but i'm not good at physics and can't get the right answer.

Any help would be appreciated.

 

[k02033]

the total energy of the ride doesnt change. it just converts more and more of its potential energy to kinetic energy. the spring has to absorb this energy.

energy absorbed by spring = total energy of ride = mgh

m = 1500kg
g = 9.8 m/s^2
h = 4.3m

the spring is 0.8 m above the floor, so h shoudl be 4.3-0.8
or you can just simply say the spring has to absorb the kinetic energy for which the ride impacts the springs with, which is just the answer to part b.
all this assumes length of compression of spring is negligible.

 

[k02033]

the length of the compression of the spring i assumed was 0.8m

But the spring starts to absorb the ride's KE when its 0.8 m above the ground.

 

[k02033]

if you use your formulas :

energy absorbed by spring = total energy of ride = mgh

m = 1500kg
g = 9.8 m/s^2
h = 4.3m

it as if the springs were on the floor, and the ride has fallen through 4.3m before it impacts the springs. which is not true

 

[k02033]

oh yes you are right, sorry i forgot the red term, i kept thinking compression length was neglible