PHY2048 Exam 1 Review, Fall 2016
1. If the x component of vector A is 20.0 and the angle it makes with the positive x axis is
30.0 degrees, then what is the y component?
a. 11.5
b. 34.6
c. 30.0
d. 20.0
2. A cube of edge length 5 sits with one corner at the origin of an xyz coordinate system(
refer to figure 2) A vector starts at the origin, extends through the center and ends at
another corner. Express the vector in unit-vector notation.
a. 5i+10j+15k
b. 0i+5j +5k
c. 5i+5j+5k
d. 25i+25j+25k
3. What is 3C∙(2A×B) if
A = 1i +2j+3k
B=-3i+4j+2k
C=9i-10j
a.170
b.-260
c.940
d.-380
PHY2048 Exam 1 Review, Fall 2016
4. A motorist drives along a straight road at a constant speed of 80 m/s. At t = 0 she
passes a parked motorcycle police officer, and the officer takes off after her with
acceleration, a(t) = bt, where b is a constant and t is the time (i.e., the acceleration
varies linearly with time). If the officer maintains this rate of acceleration, what is the
speed of the police officer when he reaches the motorist (in m/s)?
a. 120m/s
b. 180m/s
c. 30m/s
d. 90m/s
5. A ball is shot from ground level toward a wall at distance x. Figure 5 shows the y
component vy of the ball’s velocity just as it would reach the wall, as a function of that
distance x. The scaling is set by vys=5m/s and xs=20m. What is the launch angle?
a. 31.7 degrees
b. 14.3 degrees
c. 89.5 degrees
d. 10.1 degrees
6. In the overhead view of Fig. 6, Jeeps P and B race along straight lines, across flat terrain
and past stationery border guard A. Relative to the guard, B travels at a constant speed
of 20 m/s at the angle theta 2 = 20 degrees. Relative to the guard, P has accelerated
from rest at a constant rate of 0.4m/s^2 at the angle theta 1 = 60 degrees. At t=10s, what
is the velocity of P relative to B in unit vector notation.
a. 14.8i +27.1j
b. 16.3i+2.1j
c. 18.3i+4.6j
d. -16.8i+-3.4j
PHY2048 Exam 1 Review, Fall 2016
7. A crate of mass m is stationary on a ramp at an angle of 20°(Figure 7). What is the
minimum coefficient of static friction between the crate and surface for this to be
possible?
a. 1
b. 0.8
c. 0.4
d. 0.6
8. In Figure 8, a 1.2kg ball rotates with a vertical rod. The ball is connected to two massless
strings each of length 1.7m. The strings are also connected to the vertical, rotating rod.
The strings are tied to the rod with seperation d=1.7m and are taut. The tension in the
upper string is 35 Newtons. What is the speed of the ball?
a. 7.5m/s
b. 10.2m/s
c. 14m/s
d. 6.5m/s
9. Two blocks of mass m 1 and m2 are set up as shown in Figure 9. If m 1 = 10 kg, m2 = 10
kg, θ = 30°, and μk = 0.5, they begin to move after being released from rest. How long
will it take for the blocks to move 1 m?
a. 1.8s
b. 9.2s
c. 2.5s
d. 8.7s
PHY2048 Exam 1 Review, Fall 2016
Bonus: Block B has mass m and is released from rest when it is on top of cart A, which has a
mass of 3m. Determine the tension in the chord CD needed to hold the cart from moving while B
slides down. The angle between the incline and the positive x axis is 𝜃. The coefficient of kinetic
friction is μk. Refer to Figure 10.
a. cos(𝜃)(-μkmgcos(𝜃)+mgsin(𝜃))
b. cos(𝜃)sin(𝜃)μk
c. sin(𝜃)(-μkmgcos(𝜃)+mgsin(𝜃))
d. sin(𝜃)(μkmgcos(𝜃)+mgsin(𝜃))