Answer:
option (E) is correct.
Explanation:
Work done is defined as the product of force and the distance in the direction of force.
force, f = 100 N
Coefficient of friction, = 0.25
distance = 15 m
So, net force F = f - friction force
F = 100 - 0.25 x m g
Work = (100 - 0.25 mg) x d cosθ
For minimum work, the angle should be maximum.
So, the value of θ is 76°.
thus, option (E) is correct.
<span>B. equal and in opposite directions</span>
Answer:
4 seconds
Explanation:
Given:
v₀ = 20 m/s
v = 0 m/s
a = -5 m/s²
Find: t
v = at + v₀
0 m/s = (-5 m/s²) t + 20 m/s
t = 4 s
Answer:
a) m = 69.0 kg
b) release some gas in the opposite direction to the astronaut's movement
Explanation:
a) Let's use Newton's second law
F = m a
m = F / a
m = 60.0 / 0.870
m = 69.0 kg
b) when we exert a force on the astronaut it acquires a momentum po, as the astronaut system plus spacecraft is isolated, the momentum is conserved
p₀ = p_f
m v = M v '
v ’=
so we see that the ship is moving backwards, but since the mass of the ship is much greater than the mass of the astronaut, the speed of the ship is very small.
One method to avoid this effect is to release some gas in the opposite direction to the astronaut's movement so that the initial momentum of the astronaut plus the gas is zero and therefore no movement is created in the spacecraft.
Answer:
A ratio of equivalent units
Explanation:
A conversion factor is a ratio of equivalent units and depends on which units are to be converted.
For example we want to convert 275 [mm] to inches, so we have to find the right conversion factor to allow us to work that conversion.
275 [mm] = inches = ?
![275 [mm] * \frac{1in}{25.4mm} = 10.82 [in]](https://tex.z-dn.net/?f=275%20%5Bmm%5D%20%2A%20%5Cfrac%7B1in%7D%7B25.4mm%7D%20%3D%2010.82%20%5Bin%5D)
In this case the ratio is 1/25.4 = 0.039 [in/mm]