Problems Based on Motion

Q.1. If a car is moving with a speed of 100 km/h for one hour and for next one hour car is moving with a speed of 80 Km/h. Find the average speed of car in km/h and meter/sec ?

Sol. Given V1 = 100 km/h V2 = 80 km/h

Average Speed = ( V1 + V2 )/ 2 ( Because the time interval is same )

= ( 100 + 80 ) / 2

= 180 / 2

= 90 km/h

For converting from km/h to m/sec multiply with 5/18

Average velocity = ( 90 * 5 ) / 18

= 25 m/sec

Q.2. If a car is moving with a speed of 64 km/h for one hour and for next one hour car is moving with a speed of 44 Km/h. Find the average speed of car in km/h and meter/sec ?

Sol. Given V1 = 64 km/h V2 = 44 km/h

Average Speed = ( V1 + V2 )/ 2 ( Because the time interval is same )

= ( 64 + 44 ) / 2

= 108 / 2

= 54 km/h

For converting from km/h to m/sec multiply with 5/18

Average velocity = ( 54 * 5 ) / 18

= 15 m/sec

Q.3. If a car is starting moving with a speed of 40 m/sec and if the acceleration is 4 m/sec. Find the speed after 10 sec and also find the distance after 10 sec?

Sol. Given u = 40 m/sec a = 4 m/sec t = 10 sec

We know that

V = u + a t

= 40 + 4 * 10

= 40 + 40

= 80 m/sec

S = u t + ½ * a * t^2

= 40 * 10 + ½ * 4 * 10^2

= 400 + 2 * 100

= 400 + 200

= 600 m

Science-ncert-solution

Q.4. If a car is start moving from rest and get a speed of 40 m/sec. Find the distance after 10 sec?

Sol. Given u = 0 m/sec v = 40 m/sec t = 10 sec

We know that

V = u + a t

V = a t ( because u = 0 )

a = v / t

= 40 / 10 m/sec^2

= 4 m/sec^2

S = u t + ½ * a * t^2

s = ½ * a * t^2 ( because u = 0 )

= ½ * 4 * 10^2

= 2 * 100

= 200 m

Q.5. If a car is moving with a speed of 72 km/h and after applying break the speed decreases 54 km/h in 5 sec. Find the acceleration.

Sol. V = 60 Km/h = (72 * 5)/18 = 4 * 5 = 20 m/sec

u = 54 Km/h = (54 * 5)/18 = 3 * 5 = 15 m/sec

a = ( v – u ) / t

= ( 20 – 15 ) / 4

= 5 / 5

= 1 m/sec^2

Q.6. If a ship cross a river in 40 sec with a average speed of 40 m/sec and return in 40 sec with same speed. Find the distance covered by ship and also find the Average Velocity of the ship.

Sol. Total time taken = 80 sec

Average Speed = 40 m/sec

Average Speed = total distance covered / total time taken

Total distance covered = Average speed * Total time taken

= 40 * 80

= 3200 m

Average Velocity = Total Displacement / Total Time

= 0 / 80 = 0 m/sec ( Ship returns its starting point so displacement is zero )

Milan Tomic

Hi. I’m Designer of Blog Magic. I’m CEO/Founder of ThemeXpose. I’m Creative Art Director, Web Designer, UI/UX Designer, Interaction Designer, Industrial Designer, Web Developer, Business Enthusiast, StartUp Enthusiast, Speaker, Writer and Photographer. Inspired to make things looks better.