im doing my physical science over the summer and i need some help...PLEASE?

Question

If the force of a hammer on a stake is 10 Newtons and the mass of the stake is 5 kg, what will be the acceleration of the stake? CHOICE A) no acceleration CHOICE B) 2 meters per second squared CHOICE C) 1/2 meter per second squared CHOICE D) none of these

QUESTION 2: why will the acceleration of the hammer be less than the acceleration of the stake?
A)the mass of the hammer is greater than the mass of the stake
B)the mass of the stake is greater than the mass of the hammer
C) none of these

Answer 1

1. To answer a force-mass question, you pretty much always use Newton's 2nd law: F = mA. Here, the force is 10 Newtons, and the mass is 5 kg, so:

10 = 5 A
2 = A. That would be 2 meters/second/second, or choice B.

2. I think this is a messed-up question. The acceleration of the hammer and the stake should be identical (so long as the hammer and stake move together). Maybe they're trying to say that the hammer splits the head of the stake and keeps moving faster than the stake? Sounds bogus to me.

BUT, if that's the case, consider that the force acting on the stake is equal and opposite to the force acting on the hammer. OK, so F = mA. Call the acceleration of the stake A(s) and the acceleration of the hammer A(h), and the mass of the hammer to be m(h).

10 = 5 * A(s) = 2
10 = m(h) A(h)
m(h) = 10 / A(h)

But, we know A(h) < 2 (from the problem statement), so
10 / A(h) > 10 / A(s)

From that we know that m(h) = 10 / A(h) > m(s) = 10 / A(s)
m(h) > m(s), so the mass of the hammer is greater than the mass of the stake. They must be looking for choice A, but I still think it's a hokey question.

Answer 2

el jefe is right about question 1. For #2, B is definitely not the answer because if the same force is acting on two objects, the one with the smaller mass will have the greater acceleration. The only way to answer this problem is to assume that the hammer weighs more than the stake. Assuming that, here is how you do the problem:
Take fh = force on hammer = 10 N fs = force on stake = 10N
ah = acceleration of hammer as = acceler. of stake = 2 m/s/s
mh = mass of hammer ms = mass of stake = 5 kg.
So we know that fh = fs. fh = (mh)(ah) so ah = (fh) / (mh) = (fs) / (mh) since fh = fs. Also as = (fs) / (ms). Now, since mh is greater than ms, ah will be less than as. But the only way to do this problem is if you know that the mass of the hammer is greater than the mass of the stake.