help with easy physics word problems? please

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caprica1

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Hello everyone! Im really terrible at physics. My professor offered to give extra points to anyone who corrected questions they got wrong on the test.
I genuinely tried doing them(looking for similar examples in the book and such), but am still stuck. If someone could point me in the right direction, I'd appreciate it.

1) A car is making a 12 mile trip. It travels the first 8.0 miles at 30mph and the last 4.0 miles at 60mph. What is the car's average speed for the entire trip?
I got 40mph. This is what I did 0.66666(30) + 0.33333(60) = 40mph.
But it was marked wrong.

2) A car is moving with constant acceleration. At t = 5.0 its velocity is 8.0m/s and t=8.0s its velocity is 12.0m/s. What is the distance traveled in that interval of time?

3) To move a large crate across a rough floor, you push on it with a force F at an angle of 21 degrees below the horizontal. Find the force necessary to start the crate moving, given that the mass of the crate is 32 kg and the coefficient of static friction between the crate and the floor is 0.57
 
wow that is easy, but i'm too lazy to do it, thats the same stuff i learn last week in physics in highschool
 
it seems your all 3 posts are physics problems. why don't you just go to your school's tutor to build up your foundation? you shouldn't ask for hints for every single one. :meanie:
 
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