When you are driving in the forward direction, the angular velocity of the wheels ofyour car is towards:

a. your left

b. your right

c. the front
d. your left for wheels on left side, and your right for wheels on right side

Practice Questions:

1.1
When a car moves forward, the angular velocity of the wheels is directed:
a. toward the front
b. toward your right
c. toward your left
d. upward

1.2
A bicycle moves forward. The angular velocity vector of its wheels points:
a. upward
b. to the rider’s left
c. to the rider’s right
d. backward

1.3
A wheel rotates clockwise as seen from the right side. The angular velocity vector points:
a. out of the page
b. into the page
c. upward
d. downward

1.1 → c (toward your left)
1.2 → c (to the rider’s right)
1.3 → b (into the page)

A fan of diameter 120 cm is spinning at 6.00 rad/s. What is the linear speed of the
tip of its blades?
a. 7.20 m/s
b. 3.60 m/s
c. 720 m/s
d. 20.0 m/s

2.1
A fan of diameter 100 cm spins at 4.0 rad/s. What is the linear speed of the tip?
a. 2.0 m/s
b. 4.0 m/s
c. 6.0 m/s
d. 8.0 m/s

2.2
A wheel of diameter 80 cm rotates at 5.0 rad/s. What is the speed of a point on the rim?
a. 2.0 m/s
b. 4.0 m/s
c. 6.0 m/s
d. 10.0 m/s

2.3
A rotating disk has radius 0.50 m and angular speed 8 rad/s. What is the linear speed at the edge?
a. 2.0 m/s
b. 4.0 m/s
c. 6.0 m/s
d. 8.0 m/s

2.1 Diameter 100 cm → r = 0.50 m
v = 0.50 × 4.0 = 2.0 m/s → a

2.2 Diameter 80 cm → r = 0.40 m
v = 0.40 × 5.0 = 2.0 m/s → a

2.3 r = 0.50 m, ω = 8
v = 0.50 × 8 = 4.0 m/s → b

If a truck slips on the road at a curve at a certain location, which of the following
will prevent it from slipping the next time it is going there?
a. Increasing the weight carried by the truck.
b. Reducing the weight carried by the truck.
c. Reducing the speed of the truck at the curve.
d. Increasing the speed of the truck at the curve.

3.1
If a car tends to skid on a curved road, what will help prevent slipping?
a. Increasing speed
b. Reducing speed
c. Increasing radius of curve
d. Decreasing friction

3.2
A truck slips while turning. Which change would help prevent slipping?
a. Increase velocity
b. Reduce velocity
c. Reduce friction
d. Increase mass

3.3
A car moves safely around a curve. Which factor directly provides the centripetal force?
a. Engine force
b. Friction
c. Gravity
d. Air resistance

3.1 → b (reducing speed)
3.2 → b (reduce velocity)
3.3 → b (friction)

A tire of diameter 60.0 cm rolls down an inclined street for a distance 20.0 m where
it stops after hitting a wall. By how many revolutions does it turn during this
motion?
a. 0.0943
b. 0.943
c. 10.6
d. 2.51

4.1
A wheel of diameter 40 cm rolls 10 m. How many revolutions does it make?
a. 4.0
b. 8.0
c. 12.7
d. 20.0

4.2
A tire of radius 0.25 m travels 15 m. How many revolutions occur?
a. 5.0
b. 9.5
c. 15.0
d. 19.1

4.3
A circular wheel (radius 0.5 m) rolls 25 m. Number of revolutions = ?
a. 5
b. 8
c. 12.5
d. 16

4.1 diameter 40 cm → r = 0.20 m
circumference = 2π(0.20) = 0.4π ≈ 1.257 m
revs = 10 / 1.257 ≈ 7.96 → closest b (8.0)

4.2 r = 0.25 m
circumference = 2π(0.25) = 0.5π ≈ 1.571 m
revs = 15 / 1.571 ≈ 9.55 → b (9.5)

4.3 r = 0.50 m
circumference = 2π(0.50) = π ≈ 3.1416 m
revs = 25 / 3.1416 ≈ 7.96 → closest b (8)

What centripetal force does the 60 kg driver of a car experience when his car turns on
a 100 m radius bend at 20 m/s?
a. 484 N
b. 720 N
c. 914 N
d. 240 N

5.1
What centripetal force acts on a 50 kg person in a car moving at 10 m/s around a curve of radius 50 m?
a. 100 N
b. 200 N
c. 500 N
d. 1000 N

5.2
A 70 kg driver turns at 15 m/s on a 75 m radius curve. Find the centripetal force.
a. 140 N
b. 210 N
c. 300 N
d. 420 N

5.3
A 60 kg object moves in a circle (r = 30 m, v = 12 m/s). What is Fc?
a. 144 N
b. 288 N
c. 360 N
d. 720 N

5.1 m = 50, v = 10, r = 50
Fc = 50(100)/50 = 100 N → a

5.2 m = 70, v = 15, r = 75
Fc = 70(225)/75 = 70×3 = 210 N → b

5.3 m = 60, v = 12, r = 30
Fc = 60(144)/30 = 60×4.8 = 288 N → b

A geo-stationary satellite (like the ones used in satellite TV), must have an orbit
that:
a. Passes over the equator once a day.
b. Stays above the equator all the time.
c. Passes over the North and South poles once a day.
d. May have any orbit, but must make one revolution in 24.0 hours.

6.1
A geostationary satellite must:
a. Orbit over the poles
b. Stay above the equator
c. Move faster than Earth
d. Have any orbit

6.2
Which condition is required for a satellite to remain fixed over one location on Earth?
a. Orbit at any angle
b. Orbit over equator with 24-hour period
c. Orbit faster than Earth
d. Orbit closer to Earth

6.3
A satellite that appears stationary relative to Earth must:
a. Rotate in opposite direction
b. Orbit once every 12 hours
c. Orbit once every 24 hours above equator
d. Stay at poles

6.1 → b
6.2 → b
6.3 → c

That planets move around the Sun in elliptic (and not circular) orbits was first
discovered by:
a. Newton
b. Kepler
c. Galileo
d. Copernicus

7.1
Who discovered that planets move in elliptical orbits?
a. Newton
b. Galileo
c. Kepler
d. Einstein

7.2
Which law states that planets sweep equal areas in equal time?
a. Newton’s law
b. Kepler’s 1st law
c. Kepler’s 2nd law
d. Kepler’s 3rd law

7.3
According to Kepler’s Third Law:
a. Planets move in circles
b. T² ∝ r³
c. Force depends on velocity
d. Gravity is constant

7.1 → c (Kepler)
7.2 → c (Kepler’s 2nd law)
7.3 → b (T² ∝ r³)