Riding in an elevator...force?

Question

You ( of 70 kg mass) are riding in an elevator going up with an acceleration of 3 m/s ^2. How much force does the elevator's floor exert on you?

b) Answer the same question when the elevator is moving down with the same acceleration.

Answer 1

hi
basic formula to be used here is f=ma
here we have 2 scenarios elevator going up(against gravity of earth denoted by 'g' which is constant eual to 9.8 or lets say 10m/s ^2.
now when elevator is going up means it has to defy gravity and go up which means there has to be more force to accomplish
hence we use f=70 x (g+a)
which is f= 70 x(10+3)=910N
while the elevator is moving down it doesnt need to defy gravity and hence the force required to accomplish this will be much less
hence we use f=70x (g-a)
which is f=70x(10-3)=490N

is the elevator is standing still then
f=m x a
which is f= 70 x 3 = 210n

Answer 2

When you are going up the force by the elevator is F, say.
F = Gravity + mass X acceleration = (70 Kg weight) +(70X 3 Newtons)
=70 X 9.81 + 210= 896.7 newtons

When you are going down:
G-F = m x A where G is gravitational force, F is the force by the elevator, m is the mass and A is the acceleration. As we know G is 70 X 9.81 Newtons
70 X 9.81 - F = 70 X 3 where everything is in newtons.
F= 70 X 6.81= 476.7 newtons.

Answer 3

the total weight when the elavator is moving up will be the gravitational acceleration+upward velocity

and the downward weight will be gravitational acceleration-inverse movement(downward movement)

the values to deal with are the 70kg mass converted into gravitational acceleration will be 70*9.8m/s=686
upward/downward velocity =3m/s^2

thus your weight while the elavator is going up will be
9.8m/s(which is at standstill)+the upward acceleration
"remember this is because the movement is opposite the gravitational force thus increasing the gravitational pull eventually the weight"
so:
9.8m/s^2+3m/s^2=12.8m/s^2
the resaultant weight =(12.8*70)/9.8
=91.428571428571428571428571428571kgs when going upwards

now when going downwards the inverse sing applies from plus to minus
=9.8-3=6.8m/s^2

the resaultant weight going downwards =(6.8*70)/9.8

=48.571428571428571428571428571429 kgs

Answer 4

a)
F = 70(3 + 9.80662)
F = 844.634 N

b)
F = 70(9.80662 - 3)
F = 424.634 N