|01-04-2013, 03:56 AM||#1|
Join Date: Dec 2012
cheack my answaers thanks !
(1) A person can survive a feet first impact at a speed of about 1ms on concrete 15ms on soil and 34 on water. Why the different values for different surfaces?
The more the velocity the more the force of impact. The harder the surface the less the velocity, therefore the force would be less.
(2) Automobiles in the past times were manufactured to be as rigid as possible, whereas modern autos are designed to crumple upon impact why ?
Modern auto’s are done like this to increase the time of impact. Which decreases the force of impact.
(3)Bronco dives from a hovering helicopter and finds his momentum increasing, does this violate the conservation of momentum? Explain.
Yes as an external force is acting on him hence his momentum is increasing his momentum . Momentum is only conserved when there is no external force acting on the system.
(4)if a mack truck and a Mini Cooper have a head on collision which vehicle will experience the greater force of impact ? the greater impulse ? the greater change in momentum ? the greater deaccelaeration ?
The one with the lower mass will experience the greater deacceleration . momentum is conserved . (not sure )
(5) Superman meets an asteroid in outer space and hurls it at 800 ms as fast as bullet. The asteroid is a thousand times more massiv than super man. In the comic superman is seen at rest after the throw. Taking physics into account what would be his recoil velocity ?
(6) two people who weigh th same climb a flight of stairs. The first person climbs the stairs in 30s, and the second person climbs them in 40s. Which person does more wor? Which uses more power ?
Work= force x distance
The person with the 40 sec time uses less power, therefore has done less work. The person with 30 sec has more power more work.
(7) Belly- flop Bernie dives from atop a tall flagpole into a swimming pool below. His potential energy at the top is 10000J ( relative to the surface of the pool). What is his kinetic energy when his potential energy reduces to 1000 j?
(8)in the hydraulic machine, it is observed that when the small piston is pushed down 10 cm, the large piston is raised 1cm. If the small piston is pushed down with a force of 100 N, what is the most weight that the large piston can support ?
Work = force x distance 100x 0.10= 10 J ( not sure )
can some1 cheack my answears and give the right answears for the wrong answear ?
|01-04-2013, 07:15 AM||#2|
Join Date: Jun 2010
For impulse: consider that impulse = F delta T.
Change in momentum: Consider F delta t = m delta v.
Greater deceleration: you have that correct.