On an ice skating rink, a girl of mass 50 kg stands stationary, face to face with a boy of mass 80 kg. The children push off of
2 answers:
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Answer:
t=0.704s
Explanation:
A child is running his 46.1 g toy car down a ramp. The ramp is 1.73 m long and forms a 40.5° angle with the flat ground. How long will it take the car to reach the bottom of the ramp if there is no friction?
from newton equation of motion , we look for the y component of the speed and look for the x component of the speed. we can then find the resultant of the speed
Vy^2=0+2*9.8*1.73sin40.5
Vy^2=22.021
Vy=4.69m/s
Vx^2=u^2+2*9.81*cos40.5
Vy^2=25.81
Vy=5.08m/s
V=(Vy^2+Vx^2)^0.5
V=47.71^0.5
V=6.9m/s
from newtons equation of motion we know that force applied is directly proportional to the rate of change in momentum on a body.
f=force applied
v=velocity final
u=initial velocity
m=mass of the toy, 0.046
f=ma
f=m(v-u)/t
v=u+at
6.9=0+9.8t
t=6.9/9.81
t=0.704s
Answer: His average speed in mph over the last 400 m is 7.7 m/s.
Explanation:
Given: Hicham El Guerrouj of Morocco holds the world record in the 1500 m running race. He ran the final 400 m in a time of 51.9 s.
We know that , speed =
Here , distance = 400m and time = 51.9 s
Then, speed =
Hence, his average speed in mph over the last 400 m is 7.7 m/s.
Answer:
Explanation:
height of pole = 15 ft
height of man = 6 ft
Let the length of shadow is y .
According to the diagram
Let at any time the distance of man is x.
The two triangles are similar
15 y - 15 x = 6 y
9 y = 15 x
Differentiate with respect to time.
As given, dx/dt = 4 ft/s
ft/s
Answer:
The value of total energy needed per minute for the humidifier = 77.78 KJ
Explanation:
Total energy per minute the humidifier required = Energy required to heat water to boiling point) + Energy required to convert liquid water into vapor at the boiling point) ----- (1)
Specific heat of water = 4190
The heat of vaporization is = 2256
Mass = 0.030 kg
Energy needed to heat water to boiling point =
Energy needed to heat water to boiling point = 0.030 × 4.19 × (100 - 20)
Energy () = 10.08 KJ
Energy needed to convert liquid water into vapor at the boiling point
= 0.030 × 2256 = 67.68 KJ
Thus the total energy needed E = +
E = 10.08 + 67.68
E = 77.78 KJ
This is the value of total energy needed per minute for the humidifier.