Answer:

Explanation:
Data:

Calculation:
This is a perfectly inelastic collision. The two carts stick together after the collision and move with a common final velocity.
The conservation of momentum equation is

Velocity =displacement
Change in time
D=72km/hr
Time=20s
But the S.I unit of velocity is m/s so you woul have to change 72km/hr to m/s
Changing 72km to m
1 kilometer=1000meters
Then, 72 kilometers =?
72•1000/1
=72000m
Changing 72hours to seconds
If 1 hour = 3600 seconds
Then 72 hours=?
72•3600/1
=259200 seconds
Velocity =displacement
Change in time
V= 72,000
259,2005
=0.028m/s
Frequency= speed/ wavelength
=0.5m/s divided 0.1.m
=5.0 Hz
The answer would be letter D.
The answer is C) A girl hangs by both hands, motionless, from a trapeze.