PHY 1151
Summer 2002
First Hour Exam
June 14, 2002

Possibly useful information:

s = si + vi t + (1/2) a t2
v = vi + a t
v2 = vi2 + 2 a (s - si)
sin = opp/hyp
F = m a
F12 = – F21
fs,max = µs n
fk = µk n
g = 9.8 m/s2 10 m/s2

Statistics:

High: 98

Mean: 50

Low: 18?

1. A car starts from rest and accelerates at a constant 4.2 m/s2.
a) How far has it gone when its speed is 35 m/s?
b) Convert 35 m/s to a speed in units of km/h.

2. A ball is thrown from a third-floor balcony, 7.0 m above the parking lot below. The ball is thrown with an initial velocity of 10 m/s, at an angle of 37° above the horizontal.
a) What are the horizontal and vertical components of the ball’s initial velocity?
b) How long is the ball in the air, before it strikes the parking lot below?
c) How far from the building does the ball strike the parking lot below?

3. Consider a 20-kg mass suspended as shown:

Find the tension in each of the three cords shown above.

4. A 2 kg block sits on a smooth (frictionless) plane inclined 20° above the horizontal. It is connected by a string to a 5 kg mass that hangs suspened from the other end of the string as shown in the sketch above.
a) Draw clear, complete “free-body” diagrams showing all the forces on the two masses.
b) Apply Newton’s Second Law, F = m a, to the two masses and find the acceleration of the system.

5. A 2-kg block slides down a plane inclined at 20° from the horizontal as shown in the diagram above. The coefficient of sliding friction between the block and the plane is µ = 0.2.
a) Make a good, clear, complete “free-body diagram” showing all the forces on the 2–kg mass.
b) Apply Newton’s Second Law, F = m a, to the masse and find the acceleration of the block down the inclined plane.
c) How fast will the block be moving when it has traveled 1.0 m down the plane?