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QUESTION: 1

If 1 newton of force displaces a body by 1 m, the work done is

Solution:

One joule equals the work done ( or energy expended) by a force of One Newton (N) acting over a distance of one meter (m). One Newton equals a force that produces an acceleration of one meter per second (s) per second on a one Kilogram (Kg) mass. Therefore, one joule equals one Newton meter.

QUESTION: 2

A load of 50 kg is pulled upward by 5 m. The work done by the external force is (g = 10 m/s^{2})

Solution:

QUESTION: 3

A mass is moving 5 m/s with speed of along the x-direction on a smooth surface, when a force of 5 N acts on it along they-axis. The work done by against the force is

Solution:

as force is perpendicular to displacement.

QUESTION: 4

An object of mass 1kg has a PE of 1J relative to the ground when it is at a height of:

Solution:

Given:

Mass of the Body (m) = 1 Kg.

Potential energy (E) = 1 Joule.

Acceleration Due to Gravity (g) = 9.8 m/s²

Explanation:

Potential Energy:-

Potential energy is the energy which a body posses due to virtue of Position.

Formula of Potential energy

P.E = Mgh

M denotes Mass of the Body.

g denotes Acceleration Due to Gravity.

h Denotes the Height to which the body is raisen.

From Potential energy Formula,

⇒ P.E = Mgh

⇒ E = M x g x h

⇒ E = 1 kg x 9.8 m/s² x h meters

⇒ E = 1 x 9.8 x h

⇒ E = 9.8 x h

∵ [ Potential Energy = 1 joule.]

Substituting,

⇒ 1 = 9.8 x h

⇒ h = 1/9.8

⇒ h = 10/98

⇒ h = 0.102 Meters.

So, The Height at which Potential Energy is 1 joule is 0.102 meters.

QUESTION: 5

A bullet entering a metal block of 30 cm length stops on reaching 25 cm. The energy with the bullet will be lost

Solution:

QUESTION: 6

A flying aeroplane possesses

Solution:

QUESTION: 7

A tank contains water of mass ‘m’ to a height ‘h’. The potential energy associated is

Solution:

Height will be upto the centre of gravity of tank, so P.E. = mgh

QUESTION: 8

Two particles of masses 1 g and 4 g have equal kinetic energies. What is the ratio between their momenta?

Solution:

QUESTION: 9

One kWh is

Solution:

QUESTION: 10

A force of 10 N displaces a body by 6 m in 3 seconds. The power of the agency applying the force is

Solution:

We know, Power :-

= force * displacement/Time

Force is 10 N, displacement = 6 m

Time = 3 s

Then, power = 10*6/3 => 10 * 2 ⇒ 20W

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