Physics Midterm Review
1. After a rock that is thrown straight up reaches the top of its path and is starting to fall
back down, its acceleration is
10m/s2 which is gravity. The acceleration is always gravity of something falling.
2. What is Friction?
Force that obstructs motion caused by irregularities in surfaces.
3. Which has more mass, a kilogram of feathers or a kilogram of iron?
Both have the same, 1 kg
4. How does acceleration of an object change in relation to its mass?
Inversely proportional
5. Gravity is about_______________________________
10m/s2
6. What does the law of inertia state?
Things in motion stay in motion, things at rest stay at rest unless an outside force acts
upon it.
7. Torque produces
Rotation
8. An unfortunate bug splatters against the windshield of a moving car. Compared to the
force of the car on the bug, the force of the bug on the car is larger, the same, or smaller?
The same according the Newton’s 3rd law.
9. Suppose you are in a car that is going around a curve. The speedometer reads a constant
30 miles per hour. What do you know about the velocity and the acceleration?
The velocity and acceleration are changing.
10. Unit of speed?
m/s
11. Suppose a small plane can fly at 170 km/h relative to the surrounding air. Suppose also
that there is a 60 km/h tailwind. How fast does the plane's shadow move across the
ground?
230 km/h
12. If you whirl a tin can on the end of a string, what does the centripetal force make the can
do?
Pull inward
13. A player hits a ball with a bat. The action force is the impact of the bat against the ball.
What is the reaction to this force?
Ball against the bat
14. The SI unit of mass is the__________
kg
15. The energy an object has by virtue of its location is its
Potential energy
16. True of False. A straight line about which rotation takes place is called an axis.
True
17. True or False. The center of mass of an object is always located at the object's geometric
center.
False
18. **A skateboarder starting from rest accelerates down a ramp at 4 m/s2 for 3 s. What is the
final speed of the skateboarder?
12 m/s
19. **A crate falls from an airplane flying horizontally at an altitude of 1750 m. Neglecting
air drag, how fast will the crate strike the ground?
187 m/s
20. **A 10,000-kg airplane in takeoff uses the 4,000 N thrust of its engine. What is the
acceleration of the plane during takeoff?
0.4 m/s2
21. **What is the work done in raising a 35-kg block 5 m vertically?
1750 J
22. **What is the friction force that must be overcome by a 375 kg box to be pushed across
the floor with a coefficient of friction of 0.55?
2062.5 N
23. **What is the potential energy of a 65 kg object that sits on a 13 meter high table?
8450 J
24. a) What is the point of contact for opening the door?
The door knob
b) About how long is the lever arm of the door?
1m
c) What is the torque of the door when opened with a force of 20 N?
20 Nm
25. How are torque and work different?
Torque produces rotation, whereas work is linear
26. The student pushes the book across the table with a Force of 45 N. The book moves 1 m
across the table. What is the torque of the book?
There is no torque because the book is not rotating
27. What is the torque of a door that has a door knob 1.5 m from the hinges and is pulled
with a force of 35 N?
52.5Nm
28. Where is the center of gravity of this object (A, B, or C)?
C
29. a) What type of equilibrium is the object currently in?
Unstable equilibrium,
b) Why?
Because if it is pushed the CG will drop
30. Stand on the X. Without moving from the X, try to pick up the basket.
a) What happened?
You fall and cannot reach the basket
b) Why?
Because your CG extends beyond your support base (feet)