Answer:
1977.696 J
Explanation:
Given;
Weight of the box = 28.0 kg
Force applied by the boy = 230 N
angle between the horizontal and the force = 35°
Therefore,
the horizontal component of the force = 230 × cosθ
= 230 × cos 35°
= 188.405 N
Coefficient of kinetic friction, μ = 0.24
Force by friction, f = μN
here,
N = Normal force = Mass × acceleration due to gravity
or
N = 28 × 9.81 = 274.68 N
therefore,
f = 0.24 × 274.68
or
f = 65.9232 N
Now,
work done by the boy, W₁ = 188.405 N × Displacement
= 188.405 N × 30
= 5652.15 J
and,
the
work done by the friction, W₂ = - 65.9232 N × Displacement
= - 65.9232 N × 30 m
= - 1977.696 J
[ since the friction force acts opposite to the direction of motion, therefore the workdone will be negative]
Answer:
Light waves slow down as they travel from gas to solid.
Explanation:
The speed of light is often quoted with reference to a vacuum. Light travels fastest in a vacuum and in a gas.
When light travels through other media such as solids or liquids, the speed of light is decreased due to absorption and scattering of photons by molecules as well as remissions.
Hence the speed of light decreases from gas to solid.
Answer:
2.837% less than actual value.
Explanation:
Based on given information let's calculate our value.
S = Vxt = 331m/s x 5s = 1655m, that is the total distance that sound would travel in 5 seconds.
1mile = 1609.34meters.
percentage error is.
negative indicates less than actual value.
Answer:
Lens at a distance = 7.5 cm
Lens at a distance = 6.86 cm (Approx)
Explanation:
Given:
Object distance u = 12 cm
a) Focal length = 20 cm
b) Focal length = 16 cm
Computation:
a. 1/v = 1/u + 1/f
1/v = 1/20 + 1/12
v = 7.5 cm
Lens at a distance = 7.5 cm
b. 1/v = 1/u + 1/f
1/v = 1/16 + 1/12
v = 6.86 cm (Approx)
Lens at a distance = 6.86 cm (Approx)
Answer:
Explanation:
= 4190 J/kg.K
= 910 J/Kg. K
= 1.50 kg
= 1.80 kg
ΔT + 
ΔT
= (1.50)(910)(85.0-20)+(1.80)(4190)(85.0-20)
= 578,955 J
= 579 kJ
