A crate of mass 40 kg sits on a level surface that has friction. An applied force of 250 N at some angle below the horizontal acts on the crate so that it moves horizontally at a constant speed. The force and its x and y components are shown in the diagram. The normal force acting on the crate will be most nearly... A. 640 N
B. 540 N
C. 390 N
D. 240 N
AND for the same crate as the previous problem, moving at constant speed, the force of friction acting on the crate must be nearly...
A. 100N
B. 200N
C. 225N
D. 500N

If gases like carbon dioxide and methane make up less than 1% of the total atmosphere, why is it important for scientists to monitor changes in percentages of these gases?

If the spring constant k of a pogo stick is 3500 n m and the weight of the person on the pogo stick is 700 n, how much is the spring in the botom of the pogo stick compressed?

During the experiment if you could triple the breakaway magnetic force with all other quantities left unchanged, what is the new value for the critical velocity if it was v0 (initial velocity), initially? (b) now if you halved the radius with all other quantities left unchanged, what is the new critical velocity if it was v0 (initial velocity), initially? (c) if during the experiment, critical velocity quadrupled with all other quantities left unchanged, what is the new breakaway force if its magnitude was initially f0,?