Answer:
C) When wind direction or wind speed changes with altitude :)
Explanation:
Answer:
The driver's average velocity is 82.35 km/h.
Explanation:
Given:
The motion of the driver can be divided into 3 parts:
i. Displacement of the driver in 1.5 hours = 135 km
ii. Rest for 45 minutes.
iii. Displacement in next 2 hours = 215 km
The direction of motion remains same (east).
Now, total displacement of the driver is,
km.
Rest time is 45 minutes. Converting it to hours, we need to use the conversion factor
hour.
So, 45 minutes in hours is equal to
hours.
Now, total time taken for the complete journey is, 
Average velocity is given as:

Therefore, the driver's average velocity is 82.35 km/h
Answer:
Explanation:
The hand provides Kinetic Energy in moving.
The KE is transformed to Frictional energy
The Frictional Energy can produce heat and light energy.
The sandpaper produces little shreds from the grit of the paper.
The shreds have KE (they move)
The unknown substance can be lithium, which has a specific heat capacity of approximately
.
Explanation:
When heat energy is supplied to a certain substance, the temperature of the substance increases according to the equation:

where
Q is the amount of energy supplied
m is the mass of the sample
is the specific heat capacity of the substance
is the change in temperature
In this problem, we have
m = 4.9 g is the mass
Q = 668.85 J is the specific heat capacity
is the change in temperature
Solving for
, we find the specific heat capacity of the substance:

Looking at tables of specific heat capacity, we can see that the unknown substance can be lithium, which has a specific heat capacity of approximately
.
Learn more about specific heat capacity:
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