Answer:
the moment of force is 25 Nm.
Explanation:
Given;
weight of the book, F = 50 N
distance through which his hand was stretched, d = 50 cm = 0.5 m
The moment of force is calculated as;
moment of force = F x r
moment of force = 50 N x 0.5 m
moment of force = 25 Nm
Therefore, the moment of force is 25 Nm.
Answer:
C.
Explanation:
A person pushing a couch will face resistive force of friction . When resistive force is greater then his force of effort , couch will not move. This force is static friction because the couch is stationary. When the force of effort is increased , magnitude of static friction also increases keeping the couch stationary. The ability of the static friction to increase its magnitude is limited by a maximum value beyond which the couch starts moving. The static friction is then converted into kinetic friction.
In rest of the three cases object is already moving so kinetic friction is in action.
Answer:
The entropy change is 45.2 kJ/K.
Explanation:
mass of water at 100 C = 2 kg
Latent heat of vaporization, L = 2260 kJ/kg
Heat is
H = m L
H = 2 x 2260 = 4520 kJ
Entropy is given by
S = H/T = 4520/100 = 45.2 kJ/K
Answer:
correct answer is option d (Light emitted by an element produces a unique identifying spectrum.)
Explanation:
Each element has different atomic number and atoms of an element can radiate a certain amount of energy. Different elements have different atomic spectrum and it can be used to determine the composition of a material.
When atoms are excited to higher energy state after some time they came back to lower state by emitting their excess energy in the form of light. This light has certain wavelength. This emitted light can be seen as a series of different colored lines and between two colored lines there is a dark space. This series of colored lines is called a line spectra or atomic spectra.
