Question
No need explanation, just the answer please
29. For the Atwood machine, at t-0 a fly of mass m lands very softly (with almost no velocity and acceleration) on the left mass M. After a certain time, the fly will take off. After the fly takes off the left mass M will (select the best answer) a. move down with uniform velocity b. move down with and acceleration equal to g c. move down with and acceleration equal to mg/(2M+m) d. move up with and acceleration equal to mg/(2M+m) e. The left mass M will not move 30. An object of mass m-1 kg is released on an incline that makes 45° with the horizontal, on a planet with the gravitational acceleration g- 2 m/s?). If the friction coefficient is 0.5, the acceleration of the object moving down on the incline will be: a) 2 m/s2 b) 0.2 m/s c) 2 m/s2 e). 0.5 m/s 31. A ball of 1 kg is moving on a horizontal surface with a constant speed of 2 m/s describing a circular trajectory of radius 4m, due to the action of a certain force F. The value of this force is: a. 1 N b. 1 kN c. 0 because the ball is moving without acceleration. d. 10 N if the gravitational acceleration is 8-10 m/s e. 0.2 N 32, A car of mass m = 1000 kg is traveling around a flat circular racetrack of radius 400 m. The static coefficient of friction between the tire and the road (against transverse motion) is = 0.1. (Assume g 10m/s). How fast can the car travel before it starts to skid? Express the speed in the units of m/s. a. 0 m/s b. 100 m/s c. 20 m/s d. 400 m/s e. 10 m/s
Explanation / Answer
29. after fly takes off.
again a = 0
so it will move with constant velocity.
Ans(a)
30. f = u N = u m g cos45
along the incline,
Fnet = m g sin45 - u mg cos45 = m a
a = (sqrt(2)) ( sin45 - 0.5cos45)
a = 0.5 m/s^2
Ans(e)
31. F = m v^2 / r = 1 x 2^2 / 4 = 1 N
Ans(a)
32. F = u m g = m v^2 / r
u g = v^2 / r
v = sqrt(0.1 x 10 x 400) = 20 m/s
Ans(C)
