What is the initial angle theta (in degrees)? a) 20.5 b) 46.4 c) 57.3 d) 81.1 Ho

Question

What is the initial angle theta (in degrees)? a) 20.5 b) 46.4 c) 57.3 d) 81.1 How long (in s) is the ball in the air? a) 2.86 b) 1.15 c) 3.12 d) 3.37 A man of mass 80 kg is in an elevator in the Burj Khalifa in Dubai (now the tallest building in the world). The elevator has a cruising speed of 8 m/s and reaches this speed at t = 4 s after starting from rest at t = 0 s. What is the man's apparent weight (in N) while the elevator is accelerating upward? Assume constant acceleration. a) 660 b) 765 c) 944 d) 1010 A cart of mass M is on the frictionless horizontal table, and is connected to a mass m with an ideal string through a massless and frictionless pulley as shown in the figure at right.

Explanation / Answer

Solution:

4.

As we know;

H(max) = v2sin2 / 2g

=> 10 = (40)2sin2 / 2g

=> sin2 = 0.125

=> = 20.5o

5.

As we know;

Time of flight = T(flight) = 2vsin/g

=> T = 2*40*sin20.7o / 9.81

=> T = 2.86 seconds

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