Answer:
(a) the high of a hill that car can coast up (engine disengaged) if work done by friction is negligible and its initial speed is 110 km/h is 47.6 m
(b) thermal energy was generated by friction is 1.88 x J
(C) the average force of friction if the hill has a slope 2.5º above the horizontal is 373 N
Explanation:
given information:
m = 750 kg
initial velocity, = 110 km/h = 110 x 1000/3600 = 30.6 m/s
initial height, = 22 m
slope, θ = 2.5°
(a) How high a hill can a car coast up (engine disengaged) if work done by friction is negligible and its initial speed is 110 km/h?
according to conservation-energy
EP = EK
mgh =
gh =
h =
= 47.6 m
(b) If, in actuality, a 750-kg car with an initial speed of 110 km/h is observed to coast up a hill to a height 22.0 m above its starting point, how much thermal energy was generated by friction?
thermal energy = mgΔh
= mg (h - )
= 750 x 9.8 x (47.6 - 22)
= 188160 Joule
= 1.88 x J
(c) What is the average force of friction if the hill has a slope 2.5º above the horizontal?
f d = mgΔh
f = mgΔh / d,
where h = d sin θ, d = h/sinθ
therefore
f = (mgΔh) / (h/sinθ)
= 1.88 x /(22/sin 2.5°)
= 373 N
Answer:
v = -0.45 m/s
Explanation:
Assuming the canoe was initially at rest with momentum L = 0
and that the dog's velocity is in the positive direction
conservation of momentum
0 = 15(1.2) + 40v
v = -0.45 m/s
The same 500N, is the Newton’s Third Law.
Answer:
Smallest drop: Water
Largest drop: Dirt
Explanation:
The heat needed to change the temperature of a sample is:
(1)
with Q the heat (added(+) or removed(-)), c specific heat, m the mass and the change in temperature of the sample. So, if we solve (1) for
Sample A:
Sample B:
Sample C:
Note that the numbers 16744, 5400, 9450 are in the denominator of the expression that gives the drop on temperature. so, if Q is the same for the three samples the smallest denominator gives the largest drop and vice versa.
So, the smallest drop is Sample A and the largest is Sample C.
(Important: The minus sign of implies the temperature is dropping)
It MUST be either glue or gravity.