Answer: 80 s
Explanation:
Speed is expressed in v= d/t, derive the equation so we can have time.
First conert km into meters to cancel out both units and only seconds will remain.
1.2 km x 1000m/ 1km = 1200 m
t = 1200 m /15 m/s = 80 s
Answer:
The power of the bulb is reduced to a quarter
Explanation:
The power in an electrical circuit is
P = V I = I² R
If the dimmer cuts the current in half
I = I₀ / 2
The resistance of the light bulb after hot is little affected by small changes in the current
We substitute in the equation
P = I₂ R
P = (I₀ /2)² R
P = ¼ I₀² R
P = ¼ P₀
The power of the bulb is reduced to a quarter
Answer:
0.124 m
Explanation:
the period of a simple pendulum with a small amplitude is given as
T = 2π [√(I/mgd)]
From the above stated formula,
I = moment of inertia
m = mass of the pendulum
g = acceleration due to gravity, 9.8 m/s²
d = distance from rotation axis due to center of gravity
Also, moment of Inertia, I = 2mr², if we substitute this in the above formula, we have
T = 2π [√(2mr²/mgd)]
If we assume that our r = d, then we have
T = 2π [√(2r/g)]
If we make r the subject of the formula in the above equation, we get
r = gT² / 8π²
r = (9.8 * 1²) / 8 * π²
r = 9.8 / 78.98
r = 0.124 m
Thus, the radius of the hoop is 0.124 m
Answer:
v₀ = 13.24 m / s
Explanation:
Let's use Newton's second law to find the average acceleration during the crash
F = m a
. a = F / m
a = 8000/73
a = 109.59 m / s²
Now we can use the kinematic equations to find the initial velocity, since when the velocity stops it is zero (v = 0)
v² = v₀² - 2 a x
v₀² = 2 a x
v₀ = √ 2 a x
v₀ = √ (2 109.59 0.80)
v₀ = 13.24 m / s
