IX--CLASS--PHYSICS WORKSHEET 4

ARMY PUBLIC SCHOOL, GOLCONDA

Class 9 – Physics - Ch 8 – Motion

(WORKSHEET - 4)

Subtopic –

·         RATE OF CHANGE OF VELOCITY- ACCELERATION

·         EQUATIONS OF MOTION.

EQUATION OF MOTION

WHERE,

t is the time interval

s is the distance moved during this time

u is the velocity at the start

v is the velocity at the end

a is the (constant) acceleration

MCQs

1.  Which of the following statements is correct?

(a) both acceleration and velocity are same
(b) acceleration is a scalar and velocity is a vector
(c) acceleration is a vector and velocity is also vector
(d) none of these.

2.  When a body moves  in uniform motion, then:-

(a) its acceleration is zero

(b) its acceleration is positive

(c) its acceleration is negative

(d) none of these.

3.  Which of the following statements is correct?

(a)speed distance are scalar, velocity and acceleration are vector

(b) speed distance are vector, velocity and acceleration are vector

(c) speed and velocity are scalar, distance and velocity are vector

(d) speed and velocity are vector, distance and displacement are scalar

4.  m/s²  is S.I. unit of-

(a)  speed                                                        (c) acceleration

(b)  distance                                                    (d) time

5.  Acceleration of a moving body can be-

(a) can be positive
(b) can be zero
(c) can be negative
(d) all are true.

6.  Acceleration = velocity x time

(a)  True

(b)  false

(c)  both (a) and (b)

(d)  Neither (a) nor (b).

7.  Acceleration = velocity/time

(a)  True

(b)  false

(c)  both (a) and (b)

(d)  neither (a) nor (b).

8.  Acceleration = (u – v)/t

(a)  True

(b) false

(c) both (a) and (b)

(d) neither (a) nor (b)

9.  Acceleration = (v –u)/t

(a) True

(b) False

(c) both (a) and (b)

(d) neither (a) nor (b)

10.     The acceleration is _________ if it is in direction of velocity and ______ if it is in direction opposite to velocity.

(a) Positive, negative

(b) Negative, positive

(c) Negative, negative

(d)  Positive, positive

Q & A’s

1.  Define acceleration and mention its formula with S.I. units..

2.  When you will say a body is in

           (a) Uniform acceleration

           (b)  Non- Uniform acceleration

3.  State which of the following situations are possible and give example of each-

(a) An object with constant acceleration but zero velocity.

(b)  A uniform speed, but still have acceleration.

(c) A uniform speed, and zero acceleration.

(d)  Acceleration is in direction of motion.

(e) Acceleration in direction opposite to motion.

(f)   An object moving in a certain direction with an acceleration in the perpendicular direction.

4.  Differentiate velocity and acceleration.

5.  What is the acceleration of a body when it is moving with uniform velocity?

Solve the following

1.   State a relations between u, v, s, a and t. what each letter denotes?

2.  A bus decreases its velocity from  80 km/h to 60 km/h in 5 s. find the acceleration of the body.

3.  A train starting from a railway station and moving with uniform acceleration attains a speed 40 km/h in 10 minutes. Find its acceleration.

4.  A motor boat starting from rest on a lake accelerates in straight line at a constant rate of 3.00 m/s² for 8.0 s. how far does the boat travel during this time?

5.  A ball is gently dropped from a height of 20 m. if its velocity increases uniformly at a constant rate of 10 m/s^{2, .}With what velocity will it strike the ground? After what time will it strike the ground?

6.  A bus starting from rest moves with a uniform acceleration of 0.1 m/s² for 2 minutes. Find

(a) The speed acquired.

(b) The distance traveled.

7.  A train is travelling at a speed of 90 km/h. brakes are applied so as to produce a uniform acceleration of -0.5 m/s^2, find how far the train will go before it is brought to rest?

8.  A trolley while going down an inclined plane, has an acceleration of 2 cm/s².What will be its velocity 3 s after the start?

9.  A racing car has a uniform acceleration of 4 m/s².. What distance will it cover in 10 s after start?

10.   A stone is thrown in a vertically upward direction with a velocity of 5 m/s^. if the acceleration of the stone during its motion is 10 m/s².In the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

IX--CLASS--PHYSICS WORKSHEET 5

ARMY PUBLIC SCHOOL, GOLCONDA

Class 9 – Physics - Ch 8 – Motion

(WORKSHEET - 5)

Subtopic –

1.) GRAPHICAL REPRESENTATION OF MOTION-

VELOCITY-TIME GRAPH

velocity - time graph (v - t graph)

(i) The velocity-time graph for a body travelling with uniform velocity is a straight line parallel to the time axis, as shown in figure 4.4 (a).

(ii) For a body starting from rest and moving with uniform positive acceleration, the v - t graph is as shown in figure 4.4 (b)

(iii) For a body starting with an initial velocity arid moving with a uniform positive acceleration, the v - t graph is as shown in figure 4.4 (c).

(iv) For a body moving with uniform negative acceleration, the v - t graph is as shown in figure 4.4 (d).

(v) For a body moving with increasing acceleration, the v-t graph is as shown in figure 4.4 (e).

(vi) For a body moving with decreasing acceleration, the v-t graph is as shown in figure 4.4 (f).

(vii) When a body thrown vertically upwards moves under gravity, the v - t graph is as shown in Fig. 4.3 (g).

The area enclosed by the velocity - time graph and the time axis for a time interval represents the displacement of the body during that time interval. The slope of the graph at any instant of time gives the acceleration of the body at that instant of time.

Q & A’s

         1.  Draw velocity-time graph for-

               (a)  A body moving with uniform velocity

               (b)  A body moving with uniform acceleration (positive)

               (c)  A body moving with non-uniform acceleration (positive)

               (d)  A body moving with uniform acceleration (negative)

               (e)  A body moving with non-uniform acceleration (negative)

               (f)   A body thrown up and then falling freely

               (g)  A body is at rest.

         2.  What can you say about the motion of an object if its speed-time graph is a straight line parallel to time axis?

         3.  Draw velocity-time graph and show that its slope gives acceleration.

         4.  What is the quantity which is measured by area occupied below the velocity-time graph?

         5.  Draw velocity-time graph and show that area under it gives distance traveled by the body in the given time interval..

         6.  Study the given graph and answer the following questions:

(a)  Which part of graph is showing acceleration?

(b)  Which part of graph shows retarded motion?

(c)  Which part of graph shows uniform motion?

         7.  An object is moving along a straight line with uniform acceleration. The following gives data of velocity at various time intervals.

Time (s)	0	1	2	3	4	5	6
Velocity (m/s)	4	8	12	16	20	24	28

      Plot velocity-time graph. From graph-

                  (a)  Velocity of object at 4 s.

                  (b)  Calculate acceleration of the object.

                  (c)  Calculate distance traveled by object in first 2 s.

         8.  The following graph is velocity time graph-

                Find-

                 (a)  Velocity of body at C.

                 (b)  Acceleration on body between A to B.

                 (c)  Acceleration on body between B to C.

                 (d)  Acceleration on body between C to D.

                 (e)  Distance travelled by object.

                  (f)   Average velocity of object.

         9.  A driver of a car travelling at 52 km/hr applies breaks and accelerates uniformly in tte opposite direction. The car stops in 5 s. another driver going at 3 km/hr in another car applies breaks slowly and stops in 10 s. on the same graph paper plot speed-time graph for the two cars. Which of the two cars traveled farther after the breaks were applied?

        10.         Study the given speed-time graph of a car and answer the following questions:

                    (a)  Find how far does the car travel in the first 4 s? shade the area on the graph that represents the distance traveled by the car during the travel.

                    (b)  Which part of the graph represents uniform motion of the car?