IB Physics A.3 Work, Energy and Power Questionbank

A machine lifts a $500\ \text{kg}$ load vertically upward at a constant speed of $2.00\ \text{m s}^{-1}$. The gravitational field strength is $9.81\ \text{N kg}^{-1}$.

A block of mass $m$ slides down a rough incline of length $L$ and angle $\theta$. The coefficient of dynamic friction is $\mu_d$. The block starts from rest and reaches the bottom with speed $v$. What is the correct expression for the energy dissipated by friction?

The energy consumption of a device is shown by the Sankey diagram below:

What is the efficiency of this device?

A $2.5\ kg$ object is attached to a spring ($k = 400\ N\ m^{-1}$) and compressed $0.30\ m$ on a frictionless horizontal surface. It is then released. After leaving the spring it slides onto a rough patch of length $1.2\ m$, where it travels the full $1.2\ m$ before coming to rest. What is the average resistive force exerted by the rough patch?