physics.

University of the District of Columbia

University Physics 201 Homework I Test I is on Monday Sept 12 Name_______________

Show all your work in detail. Due Sept 12. Type it and send by email to [email protected].

1. An experiment done on the Moon shows the position of a particle moving along the y-axis

varies in time according to the expression Y(t)= -50 + 100t – 20t2, where Y is in m and t is in

seconds.

(a) Determine the initial velocity, initial position and acceleration of the particle?

(b) Write an expression and draw graphs of the position and velocity as a function of time?

(c) Determine the acceleration, velocity and position of the particle at t = 10 s.

(d) What is the maximum height the object reaches and at what time does it reach this height?

2. Can the sum of two vectors A = 2 and B = 3 and C = 4 be equal to zero? Explain

3. Given the vectors N = 10 i - 6 j and M = 5i – 8 j.

(a) Draw the vector L = N - M.

(c) Find the magnitude and direction of the vector L.

4. Three displacement vectors of a croquet ball are shown in figure 1 where A = 20 m,

B=15 m and C = 20 m. Find (a) the resultant in unit-vector notation, and (b) the magnitude

and direction of the resultant displacement. Not drawn to scale.

V (m/s)

y –axis

C

B 10

30o

250

x-axis 5

20o

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Time (s)

A

Figure 1 Figure 2

5. Figure 2 displays the velocity versus time of a car in motion. What’s the displacement of the car (a) between t = 0 and 5 s, (b) t= 13 and 15 s and (c) how far is the car after 15s?

6. It took 5 s to come to a halt for a car to travel 200 m. Find its initial velocity and acceleration.

7. A ball is thrown upwards with initial velocity of 50 m/s and at the same time another ball is

released from rest from the roof of 6 m building. At what position and time do the two balls

pass each other?