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PHYSICS [1 Mark Question Answer]

Energy · ICSE STD 8 (ICSE - English Medium). 18 questions.

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[1 Mark Question Answer]

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18 questions · timed · auto-graded

Question 11 Mark
A force of $45\  N$ displace a chair by $0.5\  m$. What is the amount of work done ?
Answer
Force applied on the chair, $F = 45\  N$
Displacement of the chair, $5 = 0.5\  m$
Amount of work done, $W = F \times s$
$= (45\  N) \times (0.5\  m) = 22.5\  J$
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Question 31 Mark
State the formula used to calculate the work done.
Answer
The formula used to calculate the work done is
Work $=$ Force $\times$ displacement $W = F \times s$
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Question 41 Mark
What is the amount of work done in pushing a wall?
Answer
The amount of work done in pushing a wall is zero as there is no displacement of the wall in pushing it.
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Question 51 Mark
Name the energy stored in a compressed spring.
Answer
Elastic potential energy is stored in a compressed spring.
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Question 61 Mark
What are the two factors on which kinetic energy of an object depends?
Answer
Kinetic energy of an object depends on its mass and velocity.
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Question 71 Mark
Name the energy possessed by a flowerpot placed at the rooftop of a building.
Answer
A flowerpot placed at the rooftop of a building possesses gravitational potential energy.
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Question 81 Mark
Give an example in which potential energy gets converted into kinetic energy.
Answer
A stone dropped from a building is an example in which potential energy gets converted to kinetic energy.
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Question 91 Mark
What will be the work done by a force acting on a body if the displacement of the body is zero?
Answer
The work done by a force acting on a body is zero is the rate of doing work.
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Question 101 Mark
State the law of conservation of energy.
Answer
The law of conservation of energy states that energy can neither be created nor be destroyed but it can be converted from one form to another.
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Question 121 Mark
Define kinetic energy and give an example of a body possessing kinetic energy.
Answer
Kinetic energy of a body is the energy possessed by it due to its motion. A moving car is an example of a body possessing kinetic energy.
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Question 131 Mark
State the factors responsible for the work done by a body.
Answer
The factors responsible for work done by a body are force and displacement.
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Question 141 Mark
Calculate the potential energy of a stone weighing $2.5\ kg$ placed at a height of $6\ m$.
Answer
Mass of the stone$, m = 2.5 \ kg$
Height of the stone$, h = 6\ m$
$g = 10\ m/s^2$
Potential energy of the stone$, P.E. = mgh$
$= (2.5 \ kg) \times (10 \ m/s^2) \times (6\ m)$
$= 150\ J$
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Question 151 Mark
Calculate the kinetic energy of an object weighing $600 \ kg$ moving at a velocity of $30\ m/s.$
Answer
Mass of the object, $m = 600 \ kg$
Velocity of the object, $v = 30\  m/s$
Kinetic energy of the object, $\text{K.E}. =\frac{1}{2}\  mv ^2$
$=\frac{1}{2} \times(600 \ kg ) \times(30 m / s )^2$
$= 270000\  J$
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Question 161 Mark
Calculate the work done in pushing a cart through a distance of $10\  m$ when the force applied on it is equal to $120\  N.$
Answer
Force applied on the cart, $ F = 1230\  N$
Displacement of the car, $S = 10\  m$
Amount of work done, $W = F \times s$
$= (120 N) \times (10 m)$
$= 1200\  J$
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Question 171 Mark
A child lifts a book of mass $1\ kg$ from the table to a cupboard at a height of $2\ m$ from the floor. What is the potential energy of the book with respect to the floor?
Answer
Mass of the book$, m = 1\ kg$
Height of the book with respect to the floor$, h = 2\ m g = 10\ m/s^2$
Potential energy of the book with respect to the floor$, P.E. = mgh$
$= (1\ kg) \times (10\ m/s^2) \times (2\ m)$
$= 20\ J$
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Question 181 Mark
A ball of mass $400\ g$ is thrown at a speed of $2\ m/s$. Determine its kinetic energy.
Answer
Mass of the ball$, m = 4000\  g$
Speed of the ball$, v = 2 \ m/s$
Kinetic energy of the ball$, K.E. = \frac{1}{2} mv ^2$
$= \frac{1}{2} (400 \ g) \times (2 \ m/s)^2 = (200\ g) \times (4\ m^2/s^2)$
$= 800\ J$
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[1 Mark Question Answer] - PHYSICS STD 8 Questions - Vidyadip