Question

What can we say about the rock as it falls to Earth?

A) It accelerates as it falls.
B) It falls at a constant rate of speed.
C) It is at a constant velocity as it falls.
D) It accelerates until it reaches a peak velocity, then decelerates.
7)
Which object is accelerating?
A) A lamp standing motionless on a desk.
B) A ball on a string whirled in a circle at a constant speed.
C) A car driving straight along a highway at a constant speed.
D) A humming bird hovering perfectly still in front of a flower.
8)
The difference between speed and velocity is that
A) speed is a vector and requires a direction.
B) speed is a vector and requires a magnitude.
C) velocity is a vector and requires a direction.
D) velocity is a vector and requires a magnitude.
9)
A unit of length in the metric system is the
A) kilogram.
B) kilometer.
C) liter.
D) milliliter.
10)
Which car is accelerating?
A) a car that is unmoving
B) a car that rounds a curve at a constant speed
C) a car that travels in straight line at a constant speed
D) a car that is set to a constant speed of 60 miles per hour
11)
A car starts from rest at a stop light and reaches 20 m/s in 3.5 s. Determine the acceleration of the car.
A) 3.5
m
s2
B) 5.7
m
s2
C) 20
m
s2
D) 70
m
s2
12)
You own a high speed digital camera that can take a picture every 0.5 seconds. You decide to take a picture every 0.5 seconds of your physics teacher as she drops a watermelon off the top of the school. After you develop and analyze the pictures, you realize that the distance the watermelon falls from the teacher in each new picture is
A) the same in each picture.
B) gradually less in each picture.
C) gradually more in each picture.
D) proportional to the mass of the watermelon.
13)
While running around the track at school, Milt notices that he runs due East on the 100m homestretch and due West on the 100m backstretch. To train for the 800m event, he runs both the 100m homestretch and the 100m backstretch in 12.2 seconds. How do Milt's velocities on the homestretch and backstretch compare?
A) The homestretch and backstretch have velocities with the same magnitude only.
B) The backstretch velocity is greater in magnitude than the homestretch velocity.
C) The home stretch velocity is greater in magnitude than the backstretch velocity.
D) The homestretch and the backstretch have velocities with the same direction and magnitude.
14)
Consider the average speed of a runner who jogs around a track four times. The distance (400m) remains constant for each lap. However, each lap is run 5 seconds slower than the first. The time for each lap increases. The average speed for each lap ______________. This is an example of a(n) _____________ relationship.
A) increases, direct
B) decreases, direct
C) increases, inverse
D) decreases, inverse

Answer 1

The difference between speed and velocity is that

A) speed is a vector and requires a direction.

B) speed is a vector and requires a magnitude.

C) velocity is a vector and requires a direction.

D) velocity is a vector and requires a magnitude.

Answer 2

[1] When any body falls under gravity,the body will move in vertical downward direction towards the centre of earth under a constant acceleration called acceleration due to gravity .As per the question, the rock falls to earth.

Hence,the correct option to it is A] It accelerates as it falls.

7] When a body moves with constant speed in a circular path,it's direction changes continuously which leads to an acceleration.

Hence the correct answer to the question is C) A car driving straight along a highway at a constant speed.

8] Speed is a scalar quantity as it has only magnitude while velocity is a vector quantity as it has both magnitude and direction for its specification.

Hence,the correct answer to this question is C) velocity is a vector and requires a direction.

9]A unit of length in the metric system will be metre or its multiples.

Hence,the correct answer to the question is B) kilometer.

10] A car taking a round curve will experience an acceleration called centripetal acceleration which is required to keep the car along the circular curve.

Hence,the correct answer to the question is B) a car that rounds a curve at a constant speed

11]The initial velocity of car is u =0

The final velocity of car is v= 20 m/s

The time taken t= 3.5 s

From equation of kinematics we know that-

v=u+at

20=0×t+3.5a

`a=(20)/(3.5) m/s^2`

`a=5.71 m/s^2`

Hence,the correct answer to the question is B] 5.7.

12] Any body under free fall accelerates with acceleration due to gravity.

Hence,the correct answer to the question is C) gradually more in each picture.

13] Milt moves 100 m homestretch due east and 100 m backstretch due west.

The time taken by him is 12.2 seconds. The homestretch average velocity and backstretch average velocity are anti parallel to each other as they opposite in direction.

Hence the correct answer to the question will be the homestretch and backstretch have velocities with the same in their magnitude.

14]The distance given here is constant for each lap i.e 400 m.

It has been told that he is taking 5 seconds less in each lap.

We know that average speed is the ratio of total distance travelled to total time taken.As time is decreasing in each lap,so its average speed will be more for each lap.

Hence the correct answer to the question is C] increases and inversely.