急!!簡單力學(英文版)

1.A sign board of weight 200N is held by ywo cables as shown. Both cables make an angle of 45* with the vertical.
a.Calculate the tension T in each cable.
Consider vertical component of the tension to balance the weight
2Tcos45 = 200N
T = 200/2cos45 N
T = 141.2N
b.Determone the angle between each cable and the horizontal when the tension in each cable is 200N.
Let the angle be x
Consider vertical component of the tension to balance the weight
2(200)sinx = 200N
sinx = 1/2
x = 30 degrees.
2. A hanging magnet of weight 0.5N is attracted by another magnet horizontally so that the string makes an angle of 15* to the vertical.
a.what is the tension t the string?
Consider vertical component of the tension to balance the weight,
Tcos15 = 0.5N
T = 0.5 / cos15 N
T = 0.5176 N
b.what is the force between the magnets?
Consider the horizontal component of the tension to balance the magnetic force
Force = Tsin15 = 0.5176 sin15 = 0.1340 N
3.An airhostess is pulling her suitcase with a force of 15N.The force makes an angel of 60* to the horizontal as shown.
a.what are the horizontal and vertical components of the pulling force?
Horizontal component of the foce = 15N * cos 60 = 7.5N
Vertical component of the force = 15N * sin 60 = 12.99N
b.If the suitcase is moving at a constant velocity of 0.5m/s,what is the friction acting on it?
Since there is no acceleration, the friction equals to the horizontal pulling force = 7.5N