Question

Friction holds a 2.0 kg block at rest on a board inclined at 30° What is the (minimum) value of the coefficient of friction (u) between the block and the board? 0.30 0.58 0.87 17.0 QUESTION 32 Four balls are projected in different ways from the top of the same cliff. Ball A is simply dropped straight down, ball B is thrown upward at 10.0 m/s at 450, ball C is thrown horizontally at 5.0 m/s, and ball D is thrown downward at 8.0 m/s at 30°. Which balls take the same time to hit the ground? A and B A and Band C None - they all have different times to fall. QUESTION 33 You are setting up long folding tables for a family picnic, and your little nephew wants to help. The family cat jumps up on the table while you are carrying it, but the weight your nephew is lifting does not change. Where is the cat? At the center of gravity of the table. Right at the spot where you are lifting, Right at the spot where your nephew is lifting. QUESTION 34 In a carnival game where you strike a horizontal pad with a heavy hammer to make a metal slider move up to ring a bell, how much gravitational potential energy does the slider have at the very top, compared with halfway up? The same amount at all points. Twice as much if it's twice as high. Four times as much if it's twice as high.

Answer 1

m- N masina ng Jorso where, / mass, 2.0kg. weight, W= ng. so, Downward component along the damp, mgsino. o=30 inclination, Modnal force, N=mgeoso. So, Frictional force, Fu= UN = ungeoso. where l= co-efficient of Rsiction. At rest Fu = ng sino. ung cos O= mgsin sina. u= tano= fan 30° od, On Ma 0.58 13 Answes is - (b) U = 0.58. 32) For ball 1 A, initial vestical relocity is (8)= 0 For ball B Y usino u where , Tons u= 10.0m/s, 0 - 45 şx (MY) 10x1 12 mis (upwards) thrown horizontally, so initial it is For , vertical velocity (Myle=o. For D, = -8 sim 30 (downwards) -- 4 ms.

As, restical initial relocity is reach at ground at o Ros A anda, same time ! they nytt £gt² (g is doonorard, (ay =o) ha + 2al² t 12h & Answes is (B) A ande