Answer:
B . energy cannot be created or destroyed
Explanation:V.R of a lever is 3 means effort distance of the lever is 3 times more than the effort distance of the load. ... Efficiency of a lever is 60% means 40% of the energy is wasted due to friction as no machine is Friction less.
Answer:
K_b = 78 J
Explanation:
For this exercise we can use the conservation of energy relations
starting point. Lowest of the trajectory
Em₀ = K = ½ mv²
final point. When it is at tea = 50º
Em_f = K + U
Em_f = ½ m v_b² + m g h
where h is the height from the lowest point
h = L - L cos 50
Em_f = ½ m v_b² + mg L (1 - cos50)
energy be conserve
Em₀ = Em_f
½ mv² = ½ m v_b² + mg L (1 - cos50)
K_b = ½ m v_b² + mg L (1 - cos50)
let's calculate
K_b = ½ 2.0 6.0² + 2.0 9.8 6.0 (1 - cos50)
K_b = 36 +42.0
K_b = 78 J
L = 15cm = 0.15m
A = 0.15 × 0.15 = 0.0225
Sradiation is transfered from bottom
σ = 5.67 × 10⁻⁸ W/m²k
T = 605 c = 878k
Rate of energy transfer
Q = σ × A × E × T⁴
5.67 × 10⁻⁸ × 0.0225 × 2 × 0.8 × 878⁴
1792.17 W
