A man with mass m =96.4 kg (weight = 212.1 lbs is walking towards a patio at 2.00 m/s (4.47 mph) when, at the last moment, he realizes the sliding glass door is closed. He puts out his hand suddenly to stop himself, and comes to a halt in 90.0ms. Find the magnitude of the average force exerted on the door by his hand.

4 answers

Use the relation
Impulse = momentum change,
which means
Force * Time = Mass * Velocity
or just
F = M*V/T
How do I find the time? How is 90.0 m/s converted to seconds? Isn't that what I need to plug into the quation?
The number you were given for time T is 90 milliseconds, which is 0.09 s.

The units of time are not m/s (meters per second)
Oh gosh, can't believe I misread that. Thank you.