Focus On Physical Science: California Grade 8

Lesson 1: Combining Forces

Standards Check

1.
A(n) __________ is a push or a pull. 2.a
A)motion
B)acceleration
C)velocity
D)force
2.
The __________ is the combination of all the forces acting on an object. 2.b
A)force pair
B)inertia
C)net force
D)direction of motion
3.
Forces that cancel each other are called __________ forces. 2.c
A)neutral
B)balanced
C)inactivated
D)null
4.
When balanced forces act on an object, the net force is __________. 2.c
A)zero
B)positive
C)negative
D)increased due to friction
5.
When unbalanced forces act on an object, __________. 2.b
A)the net force is zero
B)the object accelerates
C)the object speeds up
D)friction becomes greater than the net force
6.
Newton's first law of motion states that __________. 2.b
A)when a force acts on an object, its acceleration is in the same direction as the force
B)acceleration is calculated by dividing the force exerted on an object by the mass of the object
C)an object will remain at rest or keep moving with a constant velocity unless a force acts on it
D)when a force is applied on an object, there is an equal force applied by the object in the opposite direction
7.
A ball is thrown straight up in the air. According to Newton's first law of motion, what is the reason for the ball falling back to Earth? 2.b
A)The ball exerts a force on the air surrounding it.
B)It is accelerating in the same direction as Earth's gravitational force on it.
C)The change in the ball's acceleration is proportional to the force acting on it.
D)A force has acted on it.
Grade 8
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