A person with a mass of 80 kg applies a vertical force to the ground of magnitude 2000 N, and has a braking force of 1000 N. What is the resultant acceleration of the person (magnitude only)?

(a) 19.7 ms-2
(b) 30.0 ms-2
(c) 28.0 ms-2
(d) 37.0 ms-2
(e) 48.9 ms-2

Question

A person with a mass of 80 kg applies a vertical force to the ground of magnitude 2000 N, and has a braking force of 1000 N. What is the resultant acceleration of the person (magnitude only)?

(a) 19.7 ms-2 
(b) 30.0 ms-2 
(c) 28.0 ms-2 
(d) 37.0 ms-2 
(e) 48.9 ms-2

anonymous · Answer

is this braking force horizontal? do you know?

anonymous · Answer

yeah, i'd say it's a horizontal force.

anonymous · Answer

ok so

Lets look at all the vertical forces acting on him

Force of gravity 

F = mg
F = 80 x 10 = 800N

Vertical force that he exerts

2000 N

Sum of all the vert forces = 800 + 2000 = 2800N

Now like you said assuming that the braking force is acting horizontally

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Using Pythagoras F net = 2973 N

F net = m x a

to find the resultant acceleration, rearrange for A

a = Fnet / m

a = 2973 / 80 


= 37 ms ^ - 2