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Answer:
<h2>B. 20°</h2>
Explanation:
Range in projectile is defined as the distance covered in the horizontal direction. It is expressed as R = U²sin2Ф/g
U is the initial velocity of the body (in m/s)
Ф is the angle of projection
g is the acceleration due to gravity.
Given U = 14m/s, g = 9.8m/s and range R = 15 m
we will substitute this value into the formula to get the projection angle Ф as shown;
15 = 15²sin2Ф/9.8
15*9.8 = 15²sin2Ф
147 = 225sin2Ф
sin2Ф = 147/225
sin2Ф = 0.6533
2Ф = sin⁻¹0.6533
2Ф = 40.79°
Ф = 40.79°/2
Ф = 20.39° ≈ 20°
Hence, the range is greatest at angle 20°
Three 40w lamp for 6 hours
Answer:
Explanation:
Stiffness of spring k equal to 4 lb/ft.
Unstretched length of the spring L is equal to 0.5 feet.
Weight of the collar W is 15lb
Radius of curvature of curve guide is 1 feet
length of vertical rod is 1.5 feet
Initial speed of collar when released from rest at A is 0 feet per seconds
use the energy conservation equation

Estimate the potential energy , component as position B as below

Estimate the kinetic energy , component as position A as below

Estimate the kinetic energy , component as position B as below

Substitute 20.5lb- ft for 
0.5lb-ft for 
0lb -ft for 


= 16.05ft/sec
They will become identical as if they were never broken