# physics help...urgent !

• Feb 21st 2008, 07:07 PM
checkmarks
physics help...urgent !
can anyone help me with these problems?

1. superwoman is hovering above the ground when a person free-falling goes by her at a terminal velocity of 140km/h. unfortunately the parachute doesnt open. it takes superwoman 1.9 s to realize the person is in distress - what must be her acceleration be if she is to catch the parachutist just before she hits the ground 1000m below?

2. a police car stopped has a speeder pass by at 100km/h. if the police car accelerates at 3.6 m/s^2
a) how long does it take to catcht he speeder
b) how far would the police car have to go before it catches the speeder\c) what would the police's speed be when it catches up?

please help! my test is tomorrow and these 2 problems im stuck on..
• Feb 22nd 2008, 01:13 AM
a tutor
Quote:

Originally Posted by checkmarks
can anyone help me with these problems?

1. superwoman is hovering above the ground when a person free-falling goes by her at a terminal velocity of 140km/h. unfortunately the parachute doesn't open. it takes superwoman 1.9 s to realize the person is in distress - what must be her acceleration be if she is to catch the parachutist just before she hits the ground 1000m below?

Work out the time left before the person hits the ground.

You know that superwoman, starting from rest, must then travel 1000m in this time.

You have s, u and t. You can find a by rearranging $s=ut+\frac{1}{2}at^2$

Off topic: In fact hitting two arms would be worse than hitting the ground if no time is allowed for deceleration.