Awesome, there's no race to do physics questions (unlike in maths) so I can be at work at time of posting and STILL be able to do it?
1.
x = 35
a = 2
v = 12
t = ?
x = vt - .5at^2
35 = 12t - t^2
t^2 - 12t + 35 = 0
(t-7)(t-5) = 0
t = 5 or t = 7
Question asks for shortest time => he didnt spend a second running the wrong way => 5s
2. Assuming this carries on from Q1 and he doesnt decide to take 7s
Initial speed = 2m/s
Final = 12
average = 7
3. I can't be bothered, too tired will do tomorrow =)
conservation of energy + momentum, usually physics questions dont require thinking
Although it looks very fun
4. I feel I've missed something... just want horizontal component of velocity to be 30, but then theta = 60. =/
5. In spring, Mel's house's lawn needs to be mowed once every week. In each week it grows maybe 3cm (Mel is not sure as she doesn't do it, but for order of magnitudes idc)
Therefore, it grows 0.03m in 604800s
Therefore, ~4.5*10^-8/s
Therefore, I can't estimate very well Grass Growing Time as I am in between two options
Therefore, we must conclude that d is right and that the grass grows 10 centimetres per second.