Fig 5.28 shows a non uniform rod abcd resting on a rough peg at c. r1 and r2 are the normal reactions on the rod by the peg and the wall respectively. f is the frictional force exerted by the peg on rhe rod . w is the weight of the rod .

explain why f has no turning effect on the rod .

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. but she does have devices to measure distance and time accurately. she knows her own mass is 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?