Honors Physics
Midterm Practice Problems
1. A car 3.5 m in length and traveling at a constant speed of 20 m/s is approaching an intersection. The
width of the intersection is 20 m. The light turns yellow when the front of the car is 50 m from the
beginning of the intersection. If the driver steps on the brake, the car will slow at -4.2 m/s2. If the driver
instead steps on the gas pedal, the car will accelerate at 1.5 m/s2. The light will be yellow for 3 seconds.
Ignore the reaction time of the driver. To avoid being in the intersection while the light is red, should
the driver hit the brake pedal or the gas pedal. Justify your answer with some pretty physics.
2. A 20 kg box rests on the flat floor of a truck. The coefficients of friction between the box and floor
are s = 0.15 and k = 0.10. The truck stops at a stop sign and then starts to move with an acceleration
of 2 m/s2. If the box is 2.2 m from the rear of the truck when the truck starts, how much time elapses
before the box falls off the rear of the truck? How far does the truck travel in this time?
3. A block of mass = 10 kg is at rest on an inclined plane with an angle of 30 degrees.
a. Draw a FBD including components as necessary.
b. Determine the coefficient of static friction necessary to prevent the mass from moving.
c. Assuming the coefficient of static friction is 0.4 and the coefficient of kinetic friction is 0.25,
determine the acceleration of the block down the plane.
d. If the distance the block slides down the plane is 3 meters, determine the time is takes to
reach the bottom of the ramp.
e. What speed does the object have when it reaches the ground.
f. Draw a x-t graph and a v-t graph for the block (using the x-axis is aligned along the direction of
motion).
Goal-less Problems
4. A 70 kg box is pulled by a 400 N force at an angle of 30 degrees to the horizontal. Starting from rest,
the box travels 15 m in 2.47 s.
5. Three blocks are in contact with each other on a frictionless horizontal surface. A person applies a
horizontal force of 18 N to the smallest block. (Hint: There are multiple ways to define your system
here. You could draw several FBDs for different objects.)