Phy Questions x 4, please help

8(a)
A: speed = 0ms^-1
B: 1500 (10)(110-89.3)= 0.5 (1500) v^2
v = 20.3 ms^-1
C: 1500 (10)(110-107)= 0.5 (1500) v^2
v = 7.75 ms^-1
D: 1500 (10)(110-77.9)= 0.5 (1500) v^2
v = 25.3 ms^-1
E: 1500 (10)(110-96.8)= 0.5 (1500) v^2
v = 16.2 ms^-1

8(b)
velocities in A, B, C, D & E will be smaller as energy is lost lost work done against friction during the process of rolling down.

9(a)
E = 0.5 (0.5) (10)^2 x 2 J
= 50 J

9(b)
F(10) = 50
F = 5N
so friction is 5N

3.
45km hour^-1 = 45 x 1000 / (60 x 60) ms^-1
= 12.5 ms^-1
150 x 1000 x 1000 = 12.5F
F = 1.2 x 10 ^7 N

4(a)
100km hour^-1 = 100 x 1000 / (60 x 60) ms^-1
= 27.8 ms^-1
0.5 (1250) (27.8)^2
= 482253J

4(b)
[I can't see the time needed as your photo didn't include that part of the qs... can you check the time again so that the solution above can be completed?]
Power = 482253J/ time in second

物理區樓上轉右, 謝謝.