latihan kelas 8

1.The unit of energy in SI is....
A. joule B.kilogram C.newton D. Meter
2.The tubes inside solar heating panels allow the Sun�s radiation to warm water. Why are these
Tubes blackened ?
A. Dark surface absorb radiation well
B. Dark surface conduck heat well
C. Dark surface emit radiation well
D. Dark surface reflect radiation well



3. As the object moves from point A to point D across the surface, the sum of its gravitational potential and kinetic energies ____.
a. decreases, only b. decreases and then increases
c. increases and then decreases d. remains the same
4. The object will have a minimum gravitational potential energy at point ____.
a. A b. B c. C d. D e. E
5. The object's kinetic energy at point C is less than its kinetic energy at point ____.
a. A only b. A, D, and E c. B only d. D and E

6. An object which weighs 10 N is dropped from rest from a height of 4 meters above the ground. When it has free-fallen 1 meter its total mechanical energy with respect to the ground is ____.
a. 2.5 J b. 10 J c. 30 J d. 40 J
7. During a certain time interval, a 20-N object free-falls 10 meters. The object gains _____ Joules of kinetic energy during this interval.
a. 10 b. 20 c. 200 d. 2000
8. The acceleration due to gravity on the surface of planet X is 19.6 meters per second2. If an object on the surface of this planet weighs 980. newtons,the mass of the object is
(A) 50.0 kg (C) 490. N
(B) 100. kg (D) 908 N
9.A man is pushing a baby stroller. Compared to the magnitude of the force exerted on the stroller by the man, the magnitude of the force exerted on the man by the stroller is
(A) zero
(B) smaller, but greater than zero
(C) larger
(D) the same
10. A basketball player jumped straight up to grab a rebound. If she was in the air for 0.80 second, how high did she jump?
(A) 0.50 m (C) 1.2 m
(B) 0.78 m (D) 3.1 m
11.A net force of 25 newtons is applied horizontally to a 10.-kilogram block resting on a table. What is the magnitude of the acceleration of the block?
(A) 0.0 m/s2 (C) 0.40 m/s2
(B) 0.26 m/s2 (D) 2.5 m/s2
12. The speed of a car is increased uniformly from
13. meters per second to 30. meters per second in 4.0 seconds. The magnitude of the car�s average acceleration in this 4.0-second interval is
(a) 0.40 m/s2 (c) 10 m/s2
(b) 2.5 m/s2 (d) 13 m/s2
14.A roller coaster, traveling with an initial speed of 15 meters per second, decelerates uniformly at �7.0 meters per second2 to a full stop. Approximately how far does the roller coaster travel during its deceleration?
(a) 1.0 m (c) 16 m
(b) 2.0 m (d) 32 m