Science Revision of 1st mid tem exam for 3rdPp
[1]Write the scientific term:
1. A straight line that passes by the center of curvature of the mirror to the position of another object.
[Principal axis]
2. It is the distance moved through a unit time.
[speed]
3. The physical quantity that has magnitude only and it has no direction. [scalar]
4. The point of collection of the parallel rays after being reflected from the concave mirror. [focus]
5. The change of an object position as time passes according to the position of another object.
[Motion]
6. Angle of incidence = angle of reflection
[first law of light reflection]
7. The speed when the body covers equal distance at unequal periods of time. [irregular speed]
[2]Give reason for:
1. The car cannot move inside towns all the time with uniform speed.
Bec. The speed is changed due to traffic
2. The ward AMBULANCE is written in a converted way on the ambulance car.
Bec.the image on a plane mirror is laterally inverted.
[3] Choose:
1. In the opposite figure, a body starts his motion from the point (a) to (b) then to point (c), then returned
to point (a) so the distance covered equals …………………. Meter.a
a. 120
b. 70
b30m
c
c. 50
d. Zero
40m
50m
2. The physical quantity that both magnitude and direction are necessary for identifying it is ………….
a. The quantity of matter
b. scalar quantity
c. vector quantity
3. If the uniform speed of a car is 72 km/hr. this means that its speed equals ………………………….
a. 20m/sec
b. 25m/sec
c. 18m/sec
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d. 40m/sec
4. Which of the following physical quantities are considered as scalar only ? ……………………
a. The force & time
c. The radius & the area
b. The mass & the force
`
d. The displacement & acceleration
3. Which of the following graphs (speed-time) represents the movement of an object at a constant speed ?
V
vv
a.
T
b.
T c. T
4. When the object is at the center of curvature of a concave mirror, the image is real ………………..
a. upright and diminished
b. inverted and equal to the object
c. inverted and enlarged
[5] Correct the underlined words:
1. The force is the length of the shortest straight line between two positions.[displacement]
[6] Show by drawing each of the following each of the following and write down the labels as possible:
1. The formation of the image of a body at the center of curvature of a concave mirror. [book p 36]
2. The formation of image of a body at a distance smaller than the focal length of concave mirror.
[book p36]
[7] Problems:
1. Two cars move in the same direction .if the speed of the first car is is 30 km/hr. and the speed of the
second car is 70km/hr. What is the relative speed of the second car to the observer.
a. Standing on the ground = 70km/hr
b. Sitting in the first car =V2 –V1 = 70 - 30 = 40 km/hr
c. What do you deduce from that?The relative speed depends on the observer
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2. A driver used the brakes to stop the car moved by 80m/sec. Calculate the time taken by the car to stop.
If it moves at decreasing acceleration 2m/sec2.
a = V2-V1/ ∆ t
∆ t = V2-V1/ a
∆ t = 0 – 80 / - 2 = 40 sec.
3. One of the cheetahs attacked a deer at rest, if the speed of the cheetah is 30m/s, calculate the distance
covered by the cheetah to catch the deer if the time taken is 10 sec.
D = V x t = 30 x 10 = 300 m.
4. A racer covered 50 meters northward within 30sec, then 100m eastward within 60sec, then 50m
southward within 10 sec. and then return back to the start point within 40sec. Calculate the average speed
of the racer.
D total = 50 + 100 + 50 + 100 = 300 m
T total = 30 + 60 + 10 + 40 = 140 sec.
V average = D total / T total = 300 / 140 = 2.14 m/sec
5.The displacement that is covered by a moving body through different times are recorded in the following
table:
D (m)
10
20
30
40
T (sec)
5
10
15
20
a. Represent the relation graphically
b. Calculate the velocity from the graph
V = d2 – d1 / t2 – t1 = 30 – 20 / 15 – 10 = 10 / 5 = 2 m/sec
50
25
60
30
6.An object covers 30 m northward from a to b, then 60m eastward from b to c and then 30 m southward
from c to d. Calculate:
1. The total distance moved by the object
D total = 30 + 60 + 30 = 120 m
2. The displacement done by the object (magnitude & direction)
Displacement = 60 m eastwards.
7.The opposite graph shows the motion of Adam and Mahmoud in a race between them:
1. What is the type of the speed for each.
Uniform speed
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2. Calculate the ratio between Mahmoud’s speed to Adam’s speed
V1 = 10/3 = 3.33m/sec
10
V2 = 5/3 = 1.6 m/sec
V1/V2 = 3.33 / 1.6 = 2
8.Draw the graphical representation that represent each of the following:
1 2 3 4 5 6 7 8 9
a. A body at rest
c. A body moves at increasing acceleration
d. A body moves at constant speed according to (speed-time) relation
8. If the angle between the incident light ray and the reflected light ray on a plane mirror= 120o .
Calculate the angle of incidence.
Incident angle = 120 / 2 = 60 o
10. Within 2.5 sec. the speed of the car increases from 20 m/sec to 25m/sec. While a bike moves from
rest and its speed reaches 5m/sec in one sec. Calculate:
1. The acceleration of the car and the bike
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T
A car = V2 – V1 / ∆ t = 25 -20 / 2.5 = 2 m/ sec 2
A bike = V2 – V1 / ∆ t = 5 – 0 / 1 = 5 m/sec 2
3. Which of them moved at a greater acceleration; the bike
[8]Compare between :
1. Virtual image and real image
Virtual image
It can be received on a screen
It is always inverted
Real image
It can’t be received on a screen
It is always erect (up right)
2. Two mirrors (according to the angle of reflection)
reflected on it self
angle to the incident angle
it reflected with equal
[9]What happens when:
1. The final speed of a moving body = zero
It will stop.
2. Falling light ray on the surface of a plane mirror
It will reflect with equal angle to the incident angle
3. A plane mirror is placed at the left side of the driver instead of the convex mirror
The driver can’t see the whole street behind it.
[10]Correct the underlined wards:
[……………m/sec 2.]
[…………mass………………….]
1. The measurement unit of acceleration is s/m
2. The force is from scalar physical quantities
[11] Complete:
1. The real image can be formed on a screen.
2. Distance = the speed of the body x the time, and its measuring unit is ………………………..
3. The change in the speed of the body by the time in which the change occurs is called acceleration
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4. Any straight line that passes by the center of curvature of the mirror and any point on its surface except
the pole of the mirror is called secondary axis
5. The speed of a moving body relative to the observer is called relative speed
[12] Show by experiment:
1. The determination of focal length of a concave mirror. [see book p34 or sc. Boklt. P 23
[13] What is meant by:
1. A body moves with acceleration equals zero
It moves with uniform speed.
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