**PHY 1151**

Summer 2002

**First Hour Exam**

June 14, 2002

Possibly useful information:

s = s_{i} + v_{i} t + (^{1}/_{2}) a t^{2}

v = v_{i} + a t

v^{2} = v_{i}^{2} + 2 a (s - s_{i})

sin = ^{opp}/_{hyp}

cos = ^{adj}/_{hyp}

tan = ^{opp}/_{adj}

**F** = m **a**

**F**_{12} = – **F**_{21}

f_{s,max} = µ_{s} n

f_{k} = µ_{k} n

g = 9.8 m/s^{2}
10 m/s^{2}

Statistics:

High: 98

Mean: 50

Low: 18?

**1.** A car starts from rest and accelerates at a constant 4.2 m/s^{2}.

**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?

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?