Question

b) A dog runs 100 m in 20 seconds. He then comes back half the distance in 10 seconds and stops. What is the dog's average velocity? c) A body of mass 1 kg is kept at rest. A constant force of 6 N starts acting on it. Find the time taken by the body to move through a distance of 12 m. d) Draw velocity-time graphs to represent (i) an object travelling with uniform velocity. (ii) an object travelling with uniform acceleration....​

Answer 1

Answer:

We are given a body whose mass is given as

m=1kg

This body is kept at rest so its initial velocity is given as

u=0m/s

A constant force is acting on this body whose magnitude is given as

F=6N

Now from Newton’s second law of motion we can find out the acceleration of the given mass. This can be done in the following way.

F=maa=

F

m

Inserting the value of force and mass, we get

a=

6

1

=6m/s2

We want to move this body using the above force through a distance which is given as

S=12m

So we can make use of the second equation of motion in order to obtain the time taken to move the mass through the above distance.

S=ut+

1

2

at2

Inserting the known values, we get

12=0+

1

2

×6×t2t2=

12

3

=4t=2s

This is the required value of the time. Therefore, it takes 2 seconds for the body to move through a distance of 12 m under the action of a constant force of 6N.

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Explanation:

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Answer 2

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A)Given , Mass of object, m=10 kg

Velocity of object, v=20ms

−1

Initial Kinetic energy, K

1 = 2/1

×10×20/2

=2000 J

Now, Final mass, m

2

=20 kg

Final Velocity, v

2

=10m/s

Final Kinetic energy, K

2 = 2/1

×20×10/2

=1000 J

Required Ratio = K /2

K /1= 1000/2000

=2:1

D) this is the velocity-time graph for uniform motion.

slope of this graph=velocity × time=acceleration.

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