Thermal Physics Quiz Exam!

1.

Which of the following graph represent the motion when Abby throw an apple onto the floor at 0s. (under free fall assumption)

A.

I
B.

II
C.

III
D.

IV

Correct Answer(s)
A. I
C. III

Explanation
Under free fall assumption, the object is only influence by acceleration due to gravity(9.8 m/s^2)
Hence, It will experience constant acceleration and increasing in speed when time increases.

From the speed-time graph, we can obtain
a) Instantaneous speed from Y-axis of the graph
b) Distance travelled from the area under the graph
c) Instantaneous acceleration from the gradient of graph

From the distance-time graph as well, we can obtain
a) Instantaneous distance travelled from Y-axis of the graph
b) Instantaneous speed from the gradient of the graph
c) Average speed by dividing the Y-axis value with the total time

Therefore, speed-time graph will shows a linear graph with constant gradient 9.8 and the distance-time graph will shows a concave upward graph.

Rate this question:

2.

Abby is travel from Pà Q àRàS. What is the average speed traveled by Abby?

A.

5 m/s
B.

1.380 m/s
C.

5000 m/s
D.

1380 m/s

Correct Answer
B. 1.380 m/s

Explanation
Average speed = total distance travelled / total time taken
Total distance travelled
= (2 km/hr)(1 hr) + (5km/h)(2hr) + (6km/hr)(3hr)
= 30 km (change to meter as answer required)
= 30 km x 1000km/m = 30 000 m

Total time taken
= 1 hr + 2 hr + 3 hr
= 6 hr (change to seconds as answer required)
= 6hr x 3600 s/hr = 21600 s

Therefore, Average speed = 30 000 m/ 216 000s = 1.380 m/s

Rate this question:

2

0

3.

Given point P is the pivot of the level. Determine its direction of rotation.

A.

Clockwise
B.

Anticlockwise
C.

Remain equilibrium

Correct Answer
B. Anticlockwise

Explanation
Law of moment states that when moment of clockwise rotation and moment of anticlockwise rotation is equal, then equilibrium is achieved.
Otherwise, the level will follow the direction of moment which having greater value.

Moment = Force perpendicular to the level x distance from the pivot to applied force

Clockwise moment
= (14 N)(2 m) = 28 Nm

Anticlockwise moment
= (5N)(3m +2m) + (6 N)(2m)
= 37 Nm

As the anticlockwise moment is greater than the clockwise moment, Hence, the level will undergoes anticlockwise rotation

Rate this question:

4.

Determine its direction of rotation.

A.

Clockwise
B.

Anticlockwise
C.

No rotation occur
D.

Option 4

Correct Answer
C. No rotation occur

Explanation
Law of moment states that when moment of anticlockwise rotation is equal to moment of clockwise rotation, the level will experience no rotation and remain in equilibrium form.
Otherwise, the level will undergoes rotation in the direction of the greater moment.

Moment = Force perpendicular to the level x distance from the pivot to the applied force

Clockwise moment
= (1000 N)(1 m)
= 1000 Nm

Anticlockwise moment
= (500 N)(2 m)
= 1000 Nm As

Clockwise rotational moment is equal to anticlockwise rotational moment Hence no rotation occur and the level is under equilibrium state.

Rate this question:

1

0

5.

A lit match is placed above a thermometer. State the type of thermal processes where the heat from the match reaches the thermometer.

A.

Conduction
B.

Convection
C.

Radiation

Correct Answer(s)
A. Conduction
B. Convection
C. Radiation

Explanation
Radiation can travel through vacuum;
Convection usually occur in fluid(gases and liquid);
Conduction take places in solid.

Hence, all types of thermal processes is required for the flame from match reaches thermometer.
Flame emit light which allows heat travelled by radiation reaches the metal bulb of the thermometer,
then the bulb conduct heat and passes the heat to the liquid-in-glass,
Next the liquid-in-glass experience convection and response rapidly toward the changing temperature.

Rate this question:

6.

Which process involves convection?

A.

Bread toasting under a grill
B.

Energy from the Sun warming a road surface
C.

Hot air rising to the top of a cool room
D.

Thermal energy transfer through a copper bar

Correct Answer
C. Hot air rising to the top of a cool room

Explanation
Radiation can travel through vacuum;
Conduction take places in solid matter;
Convection takes place in fluid (liquid and gases)

Rate this question:

7.

The air in a room is heated by a heater. The diagram shows the circulation of the air in the room. Which statement about the air that is heated is correct?

A.

The air contracts and becomes less dense.
B.

The air contracts and becomes more dense.
C.

The air expands and becomes less dense.
D.

The air expands and becomes more dense.

Correct Answer
C. The air expands and becomes less dense.

Explanation
Heat will cause the volume of fluid to expand/increase due to the molecules in a matter will vibrate more vigorously and create a larger space in between molecules

as density = mass/volume
then density will decreases when volume increases

Rate this question:

8.

Given the level is under an equilibrium state. Find the value of x.

A.

1.27 m
B.

0.6 m
C.

2.67 m
D.

5.93 m

Correct Answer
B. 0.6 m

Explanation
Law of moment states that when a level is under equilibrium state, Its clockwise moment is equal to the anticlockwise moment.

Moment= Force perpendicular to the level x the distance from the pivot to the applied force

Clockwise moment = (50 N )(1.4 m) =70 Nm
Anticlockwise moment
= (15 N)(1.4 m + x m) + (15 N )(1 m) + (10 N)(1.5 m + 1 m)
= 21 Nm + 15x Nm + 15 Nm + 25 Nm
= 15x Nm + 61 Nm

In equilibrium state, Clockwise moment = anticlockwise moment
70 = 15x + 61
15x = 9
x =0.6 m

Rate this question: