I don't get Physics, can you help me, also i'm a begginer
2 answers:
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Answer:
4.8 m/s
Explanation:
When she catches the train,
- They will have travelled the same distance.and
- Their speeds will be equal
The formula for the distance covered by the train is
d = ½at² = ½ × 0.40t² = 0.20t²
The passenger starts running at a constant speed 6 s later, so her formula is
d = v(t - 6.0)
The passenger and the train will have covered the same distance when she has caught it, so
(1) 0.20t² = v(t - 6.0)
The speed of the train is
v = at = 0.40t
The speed of the passenger is v.
(2) 0.40t = v
Substitute (2) into (1)
0.20t² = 0.40t(t - 6.0) = 0.40t² - 2.4 t
Subtract 0.20t² from each side
0.20t² - 2.4t = 0
Factor the quadratic
t(0.20t - 2.4) = 0
Apply the zero-product rule
t =0 0.20t - 2.4 = 0
0.20t = 2.4
(3) t = 12
We reject t = 0 s.
Substitute (3) into (2)
0.40 × 12 = v
v = 4.8 m/s
The slowest constant speed at which she can run and catch the train is 4.8 m/s.
A plot of distance vs time shows that she will catch the train 6 s after starting. Both she and the train will have travelled 28.8 m. Her average speed is 28.8 m/6 s = 4.8 m/s.
Answer:
Velocity= 19.05 m/s
Kinetic energy= 3.08 J
Explanation:
The corn possess potential energy. Feom law of conservation of energy, all the potential eneegy will be converted to kinetic energy, with negligible friction.
Potential energy, PE= kinetic energy, KE
Potential energy is given by mgh while kinetic energy is given by
Equating
Making v the subject of the formula then
Substituting 9.81 m/s2 for g and 18.5 m for h then the velocity will be
To get the kinetic eneegy, since PE=KE AND KE is
Substituting v with 19.05 and m with 0.017 kg we have
This can also be achieved by mgh since PE=KE hence 0.17*9.81*18.5=3.085245 J and the results are slightly different due to small energy losses and rounding off of values.