An example of friction being converted into heat energy is A) the sun. B) a generator. C) a Snickers bar. D) rubbing your hands
2 answers:
You might be interested in
Answer:
a) 3.37 x
b) 6.42kg/
Explanation:
a) Firstly we would calculate the volume of the metal using it`s weight in air and water , after finding the weight we would find the density .
Weight of metal in air = 50N = mg implies the mass of metal is 5kg.
Now the difference of weight of the metal in air and water = upthrust acting on it = volume (metal) p (liquid) g = V (1000)(10) = 14N. So volume of metal piece = 14 x
. So density of metal = mass of metal / volume of metal = 5 / 14 x
= 3.37 x
b) Water exerts a buoyant force to the metal which is 50−36 = 14N, which equals the weight of water displaced. The mass of water displaced is 14/10 = 1.4kg Since the density of water is 1kg/L, the volume displaced is 1.4L. Hence, we end up with 3.57kg/l. Moreover, the unknown liquid exerts a buoyant force of 9N. So the density of this liquid is 6.42kg/
Answer:
6.13428 rev/s
Explanation:
= Final moment of inertia = 4.2 kgm²
I = Moment of inertia with fists close to chest = 5.7 kgm²
= Initial angular speed = 3 rev/s
= Final angular speed
r = Radius = 76 cm
m = Mass = 2.5 kg
Moment of inertia of the skater is given by
In this system the angular momentum is conserved
The rotational speed will be 6.13428 rev/s
Answer:
amount of work done, W = 549.36 kJ
Given:
mass of a car engine, m = 2500 kg
initial velocity, u = 45 mph
final velocity, v = 65 mph
1 mile = 1609
Solution:
We know that 1 hour = 3600 s
Now, velocities in m/s are given as:
u = 45 mph = = 20.11 m/s
v = 65 mph = = 29.05 m/s
Now, the amount of work done, W is given by the change in kinetic energy of the car and is given by:
W =
W =
W =
W = 549.36 kJ
To minimize the material usage we have to have the volume requested with the minimum surface area.
The volume is:
And the surface is:
From the first equation we get:
I will use k instead of a number just for the conveince.
We plug this into the second equation and we get:
To find the minimum of this function we have to find the zeros of its first derivative.
Sx will denote the first derivative with respect to x and Sy will denote the first derivative with respect to Sy.
Now let both derivatives go to zero and solve the system (this will give us the so-called critical points).
Now we plug in the first equation into the other and we get:
Now we can calculate y:
And finaly we calculate z:
And finaly let's check our result:
The volume is:
And the surface is:
From the first equation we get:
I will use k instead of a number just for the conveince.
We plug this into the second equation and we get:
To find the minimum of this function we have to find the zeros of its first derivative.
Sx will denote the first derivative with respect to x and Sy will denote the first derivative with respect to Sy.
Now let both derivatives go to zero and solve the system (this will give us the so-called critical points).
Now we plug in the first equation into the other and we get:
Now we can calculate y:
And finaly we calculate z:
And finaly let's check our result: