Answer:
a) 113N
b) 0.37
Explanation:
a) Using the Newton's second law:
\sum Fx =ma
Since the crate doesn't move (static), acceleration will be zero. The equation will become:
\sum Fx = 0
\sumFx = Fm - Ff = 0.
Fm is the applied force
Ff is the frictional force
Since Fm - Ff = 0
Fm = Ff
This means that the applied force is equal to the force of friction if the crate is static.
Since applied force is 113N, hence the magnitude of the static friction force will also be 113N
b) Using the formula
Ff = nR
n is the coefficient of friction
R is the reaction = mg
R = 31.2 × 9.8
R = 305.76N
From the formula
n = Ff/R
n = 113/305.76
n = 0.37
Hence the minimum possible value of the coefficient of static friction between the crate and the floor is 0.37
Rock is completely immersed in hot water. By the second law of thermodynamics, thermal energy or heat is transferred from substance with higher temperature to substance with lower temperature until they come to thermal equilibrium i.e. both at same temperature.
It is given here that rock is at 20°C which is at lower temperature than water at 80°C. ∴Heat or thermal energy flows from water to rock. So, right choice is-
A. The water gives the rock thermal energy and gets no thermal energy in return.
Answer:
1.27 m
Explanation:
Distance = 192 m
number of rotations = 48
Distance traveled in one rotation = 2 x π x r
Where, r be the radius of wheel.
so, distance traveled in 48 rotations = 48 x 2 x 3.14 x r
It is equal to the distance traveled.
192 = 48 x 2 x 3.14 x r
r = 0.637 m
diameter of wheel = 2 x radius of wheel = 2 x 0.637 = 1.27 m
Answer: c)• 2/3
Explanation:
Lets say q1 and q2 are two charges with r distance far apart.
So electrostatic force
F = (k q1 q2) / r²
as k = Coulomb's constant
Now
q1' = 2q1
q2' = q2/3
Therefore the new electrostatic force
F' = (k q'1 q'2) / r²
F' = (k 2q1 q2) / 3r²
F' = 2/3 [(k q1 q2) / r²]
so F' = 2/3F
New electrostatic force is 2/3F
