Answer:
Work done.
Explanation:
The skater who lifts has to overcome the partner's weight. When lifted up by 1 meter, her potential energy increases by (mass)x(gravitational acceleration)x(1meter), which is the amount of work done.
(This all assumes lifting vertically and no other forces being part of the picture)
Explanation:
∆x=300 m×2
∆t=1.5 s
v=∆x/∆t → v=2×300/1.5 = 400 m/s
Answer:
b) 472HZ, 408HZ
Explanation:
To find the frequencies perceived when the bus approaches and the train departs, you use the Doppler's effect formula for both cases:

fo: frequency of the source = 440Hz
vs: speed of sound = 343m/s
vo: speed of the observer = 0m/s (at rest)
v: sped of the train
f: frequency perceived when the train leaves us.
f': frequency when the train is getTing closer.
Thus, by doing f and f' the subjects of the formulas and replacing the values of v, vo, vs and fo you obtain:

hence, the frequencies for before and after tha train has past are
b) 472HZ, 408HZ
Answer:
24.57 revolutions
Explanation:
(a) If they do not slip on the pavement, then the angular acceleration is

(b) We can use the following equation of motion to find out the angle traveled by the wheel before coming to rest:

where v = 0 m/s is the final angular velocity of the wheel when it stops,
= 95rad/s is the initial angular velocity of the wheel,
is the deceleration of the wheel, and
is the angle swept in rad, which we care looking for:



As each revolution equals to 2π, the total revolution it makes before stop is
154.375 / 2π = 24.57 revolutions