1.
A ball was thrown upwards and allowed to continue in its motion, which is shown by the graph below. Describe the motion of the ball in as much detail as you can.
2.
Which of the following is a vector?
Correct Answer
C. Force
Explanation
Vectors are physical quantities with magnitude and direction. A force has both magnitude and direction (e.g. Weight = mass x gravitational acceleration and acts downwards).
3.
Which of the following is true?
Correct Answer
B. If an object accelerates, there is definitely a resultant force.
Explanation
An object that does not move doesn't necessarily have no forces acting on it; it could be just that the forces are balanced.
Acceleration can only be brought about if there is a resultant force.
Action-reaction pairs of forces have to be of the same TYPE, so in fact these two are not a pair.
An object's inertia depends on its mass, which does not change no matter where it goes.
4.
Newton's First Law states that an object continues to be at rest or in a state of (a) __________ motion in a (b) __________ _____ unless acted on by a (c) _____________ ________.
What is (a)?
Correct Answer
uniform
constant
Explanation
The correct answer is "uniform". Newton's First Law states that an object continues to be at rest or in a state of uniform motion unless acted on by a force. This means that if an object is initially at rest, it will remain at rest, and if it is initially moving with a constant velocity, it will continue moving with the same velocity unless a force is applied to it.
5.
What force(s) is/are acting on an object that is floating on the surface of the sea?
Correct Answer(s)
B. Upthrust
C. Weight
Explanation
A. Tension usually occurs when there is a spring or string.
B. Upthrust is the force of the water on the object that is keeping it afloat.
C. The earth still pulls the object toward itself.
D. There is no normal contact force in this case as there is no other surface that the object is in contact with.
6.
What is the resultant acceleration of the object shown below? (W is weight)
Correct Answer
B. 1.5 m/s2 to the right
Explanation
From the diagram it can be seen that weight is 20N, which means that the object's mass: mass = W / g mass = 20 / 10 = 2kg The resultant acceleration is in the horizontal direction, since the forces in the vertical direction are balanced. Resultant force = (9 + 6) - (5 + 7) = 3N Resultant force = ma 2 x a = 3 a = 1.5 m/s^2 to the right (in the direction of the resultant force)
7.
Which graph shows an object changing direction once?
Correct Answer
C.
Explanation
A. The object moves at constant negative velocity before accelerating in the same direction (negative gradient) so its speed increases but it does not change direction.
B. The object starts from rest and accelerates in the negative direction with a negative velocity.
C. The object starts with a positive velocity, decelerates to zero velocity, then accelerates with a negative velocity (velocity changes from positive to negative).
D. The object starts with a positive velocity, decelerates to zero velocity, then accelerates to a maximum negative velocity. It then decelerates to zero again, and accelerates with a positive velocity (velocity changes from positive to negative to positive).
8.
The image below shows a truck engine pulling a trailer which is attached to it by a towbar, and the engine thrust is providing an acceleration of 0.1m/s2. The resistive force on the trailer is 5N.
Using a free body diagram of the trailer, find the tension in the towbar.
Correct Answer
105N
105 N
Explanation
The acceleration is to the right, which means that resultant force is also in the same direction. From the diagram, resultant force = T - R ma = T - R T = ma + R T = (1000 x 0.10) + 5 T = 105N
9.
Newton's First Law states that an object continues to be at rest or in a state of uniform motion in a (b) __________ _____ unless acted on by a (c) _____________ ________.
What is (b)?
Correct Answer
straight line
Explanation
Newton's First Law states that an object continues to be at rest or in a state of uniform motion in a straight line unless acted on by a force.
10.
Newton's First Law states that an object continues to be at rest or in a state of uniform motion in a straight line unless acted on by a (c) _____________ ________.
What is (c)?
Correct Answer
resultant force
net force
unbalanced force
Explanation
Newton's First Law states that an object continues to be at rest or in a state of uniform motion in a straight line unless acted on by a resultant force, net force, or unbalanced force. These forces cause a change in the object's motion, either by starting it from rest, changing its speed or direction, or stopping it altogether. In other words, if there is no resultant force, net force, or unbalanced force acting on an object, it will continue to move in a straight line at a constant speed or remain at rest.
11.
A ball is thrown vertically upwards with an initial velocity of 30.0 m/s from the top of a building that is 15.0m high. What is the total time it takes before it reaches the ground? (take g = 10m/s2)
Correct Answer
6.5s
6.5 s
6.46s
6.46 s
Explanation
Taking upwards as positive,
u = 30.0 m/s
s = -15.0m (the ball ends up 15.0m downwards which is negative)
a = -10m/s (this acts downwards which is negative)
t = ?
v = ?
Using the equation s = ut + 0.5at2,
-15.0 = (30.0)t + 0.5(-10)(t2)
-15.0 = (30.0)t + 0.5(-10)(t^2)
5t2 + 30.0t + 15.0 = 0
t2 + 6t + 3 = 0
t = 6.5s (2sf)
12.
A falling parachutist undergoes freefall acceleration. She experiences air resistance, which increases as her velocity increases.
What will happen to the magnitude of air resistance as she falls (increases, decreases, remains the same)?
Correct Answer
increases
Explanation
As she falls, the air resistance is smaller than her weight due to the small velocity at the start, and there is a resultant force that causes her to accelerate downwards. As her velocity increases, her air resistance will increase.
13.
The same parachutist continues to fall downwards. What happens to her acceleration as she falls downwards (increases, decreases, remains the same)?
Correct Answer
decreases
Explanation
As she falls, her velocity increases, which causes the air resistance to increase. Since the air resistance opposes her weight, the resultant force decreases and hence her acceleration decreases.
14.
What will happen to her velocity eventually?
Correct Answer
remains the same
constant
does not change
no change
Explanation
As her air resistance increases, it will come to a point where the air resistance is equal to her weight and there is no more resultant force. SInce there is no resultant force any longer, she will continue in a state of uniform motion in a straight line (downwards), so her velocity remains the same (this is called the terminal velocity).
The air resistance will not increase anymore since the velocity is not increasing.
15.
What is the magnitude of the resultant force on the block below?
Correct Answer
5N
5 N
Explanation
In the vertical direction, the resultant force is 4N. To find the overall resultant force, we can add the vectors as shown below:
x2 = 32 + 42
x = 5
16.
What is the SI unit of electric current, which measures the flow of electric charge in a circuit?
Correct Answer
C. Amperes (A)
Explanation
Amperes (A): This is the correct answer. The ampere, often referred to as an amp, is the SI unit of electric current. It measures the flow of electric charge through a conductor or circuit. One ampere is defined as one coulomb of charge passing through a point in a circuit per second.