Work-Energy Balance & Conservation of Energy - Example Problem 7.6-4

 

A 7-kg block is placed on a compressed spring and released from rest. The spring was compressed 20 cm and has a spring constant of 11 kN/m. Determine the velocity of the block after it has traveled up the slope for 1.2 meters. The coefficient of kinetic friction is 0.4 and θ = 30^o.

 

 

Given:

• m = 7 kg
• μ_k = 0.4
• θ = 30^o
• Δx = 20 cm
• k = 11 kN/m
• v₁ = 0

 

Find: v₂

 

Video solution:

 

The following video walks you through the solution to this problem. It is suggested that you try solving the problem first and then, if you have difficulties with the solution, watch the video for help.

 

 

Interactive solution:

 

Identify the 2 energy states that we need to solve this problem, identify a datum where the potential energy will be zero and then draw a free-body diagram of the block. Click on the figure to cycle through the results.

 

Note that you may have labeled your energy states differently and identified a different datum. This does not mean that yours is incorrect.

 

Which forces perform non-conservative work?

 

F_s
N
mg
F_fk