Help with physics please?

Question

I have been attempting this problem for a long time but no luck. I know for a fact that the answer is not 816. Can someone please explain this problem. Thanks!!!!

An extreme amusement park ride accelerates its riders upward from rest to 50.0 m/s in 7.00 seconds. Ignoring air resistance, what average upward force does the seat exert on a rider who weighs 1120 N?

Answer 1

First, find the average acceleration:

avg acceleration = [change in velocity]/time = [50-0]/7 = 7.14 m/s^2 up

Now write a balanced force equation to represent this problem. You know that the ride and gravitational forces oppose each other. Thus,

F_ride - F_gravity = F_net
F_ride = F_net + F_gravity
F_ride = m(a_net + gravity)

We know that a_net = 50/7 m/s^2 and g = 9.8 m/s^2. Now solve for the mass:

Weight = 1120 N = m*g -----> m = 1120/g = 1120/9.8 = 114.29 kg

Now substitute into the above equation and solve for F_ride:

F_ride = (114.29)(50/7 + 9.8) = 1936.33 N

The 816 N answer you got was the net force needed to accelerate 50/7 m/s^2 up. You just forgot to add the 1120 N component from the weight of the person.

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Hope this helps

Answer 2

Well, you're close. 816 N is the force needed to accelerate the person up at 50/7 m/s/s. what you forgot is that the seat is also pushing up against gravity (1120 N), so if you just add them together you'll get the right answer (~1936 N)

Answer 3

Start with F = ma
We know m = 1120
a is 50 m/s divided by 7 s which is about 7.
However, F is also fighting gravity, so we need to add 9.8, so the force upward is really about 17.

1120 * 17 should be the answer.

Answer 4

3.1322359 g's