Quiz 1b (Phys 101 - 11.30am, Spring 2005)

 

Name: ________________Answers______________________

 

1. A car is moving at a constant velocity of 30km/hr, East.

The net force (or total force) on the car is

a) 30 N, East.

b) greater than zero.

c) less than zero.

d) equal to zero. (because the velocity is constant)

e) indeterminate because not enough information is given.

 

2. You throw a ball in the air while situated on the surface of the Earth. As the ball rises, the ball's acceleration is

a) -10m/s2 down.

b) 10m/s2 up.

c) 10m/s2 down.

d) Indeterminate. It depends upon how hard you throw the ball.

 

3. The sketch shows a painting stage in mechanical equilibrium. The person in the middle weighs 50N, and the tensions in each rope are 100N. What is the weight W of the staging? 150 N

 

The net force F(net) = 100 + 100 50 W = 0 because the stage is in mechanical equilibrium.

Therefore W = 100 + 100 50 = 150 N.