Physics 213 Quiz # 3 points each Wednesday 9-27-2006

1. Given the y component of A , A_y = -3 and the direction of A u = 210°,

a. Draw A on a reference frame.

b. Find values for A_x , the x component of A, and A, the magnitude of A .

2.

3.

The ball that travels the highest will be

a. The 5 kg ball because it is lightest.

b. The 50 kg ball because it has the most momentum.

c. Both balls go the same height because their initial velocities are the same.
Gigi the dare devil gazelle leaps from the ground at an angle of 53° above the horizontal and a speed of 50 m/s. She strikes the wall 80 meters way. A is where she takes off, B is where she strikes the wall.

4.

a. Draw ref. Frame 1 pt

b. Draw motion diagrams in both vertical and horizontal directions. 1 pt

c. Mark on picture points A and B. 1 pt

d. Write down in neat column form, values for x, v_x , a_x,, y, v_y , a_y and t at each point. Also write down the equation for values of x, v_x , a_x,, y, v_y at B. 2 pts

5. How high on the wall should her landing platform be located?

6. The pilot of an airplane notes that the compass indicates a heading of due west . The airplane's speed relative to the air is 150 km /hr. If there is a wind of 30 km/hr toward the north, find the velocity of the airplane relative to the ground.

7. If a car of mass 1000 kg is travelling west with a constant speed of 20 kilometers per hour, what is the net force acting on it?

8. Two forces act on a 5 kg object as indicated in the figure at right.

F₁ = 30 N and F₂ = 15 N. Find the magnitude and direction of the acceleration of the object.

5 Points Bonus !

As a rocket is fired from a launching pad, its speed and acceleration both increase as its engines continue to operate. Explain why this occurs even though the thrust of the engines remains constant.