Review Question:
1. A ball is thrown from the roof of a 35 meter tall building. The ball is thrown at a speed of
20 m/s at 40o below the horizontal. Use kinematics to determine the speed and direction of the
ball when it is 10 meters above the ground. Use the full four step solution procedure from
Unit 1.
2. Same scenario as Question 1. This time use conservation of energy to determine the speed of
the ball when it is 10 meters above the ground.
a) Specify your system
b) Sketch a qualitative (i.e. no calculations) energy bar chart for the system when the ball is at
the top of the roof.
c) Sketch a qualitative energy bar chart for the system when the ball is 10 meters above the
ground.
d) Setup your conservation of energy equation and solve it to determine the ball’s speed when
it is 10 meters above the ground.
3. Suppose a car is traveling down a level street at 40 mph when it hits its brakes. Upon hitting
the brakes, the force of friction will slow the car to a stop over some distance. Suppose the
coefficient of friction between the wheels and the road is 0.4.
a) Look up a reasonable mass for the car.
b) Specify your system.
c) Setup your conservation of energy equation including work and solve it to determine the
distance the car travels before coming to a stop.
thythythythy
Physicshw6.docx
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