1) A balloon of total mass 840kg is rising vertically with constant speed. As a result of realeasing some ballast, the balloon immediately accelerates at 0.5m/s2. Calculate the mass of the ballast released
2)A load of weight 7kN is being raised from rest with constant acceleration by a cable. After the load has been raised 20 m, the cable suddenly becomes slack. It continues to move up 4m before coming to instantaneous rest. Assuming no air resistance, find the tension in the cable before it became slack
THanx in advance....
1)If the tension is T in the cable, using F=ma
Before ballast released
T-840g=0 so T=840g
After ballast of mass m released, the mass falls to 840-m
T-(840-m)g=.5(840-m)
840-840g+mg=420-0.5m
Make m the subject: mg+0.5m=840g -420so m(g+0.5)=-420+840g so m=(-420+840g)/(g+0.5)
2)First use suvat to find the acceleartion then F=ma to find the force
After the cable goes slack
s=4
u
v=0
a=-9.8
t
so
so
so
)
Before the cable goes slack
s=20
u=0
v=
)
a
t
so
so
Now use F=ma
T-mg=ma
T-7000=(7000/9.
*1.96 so T=8400N
