A string going over a massless frictionless pul- ley connects two blocks of masses 4.2 kg and
3.8 kg. As shown on the picture below, the
4.2 kg block lies on a 23° incline; the coefli-
cient of kinetic friction between the block and
the incline is u= 0.23. The 3.8 kg block is
hanging in the air.
The 3.8 kg block accelerates downward
while the 4.2 kg block goes up the incline
with the same acceleration.
If gravity is constant (g=9.8), what is the acceleration of the system?

Bone-strengthening physical activity done increases bone-mineral content and bone density in youth.

Which is the best predictor of the radioactive nature of an isotope? o the proton-to-electron ratio the neutron-to-proton ratio o the neutron-to-electron ratio the electron-to-proton ratio

(2) (a) you have a simple circuit that consists of only a battery (δvbat=1.5v) and two resistors with resistance r1=10ω and r2=5ω, connected in series with each other. what is the current running through the battery? (b) you re-arrange your circuit so now r2 is attached in parallel to r1 rather than in series. what is the current running through the battery? (c) you add an additional resistor r3=7ω on the same branch as r2. what is the current running through the battery? (d) what is the power dissipated in r3?