Summer Assignment Revision –Term 1 Grade:9 Answer as many as possible: 1) State universal law of gravitation. Express it mathematically. 2) Differentiate between G‘ and g‘ in tabular form. 3) (a) What is acceleration ? Write its unit. (b) Draw velocity-time graph, when an object has (i) uniformly accelerated velocity. (ii) uniformly retarded velocity. 4) Prove that if a body is thrown vertically upward, the time of ascent is equal to the time of descent. 5) The earth attracts the moon. Does the moon also attract the earth ? If it does, why does the earth not move towards the moon ? 6) A bullet of mass 10 g is fired with a velocity of 400 m/s from a gun of mass 4 kg. What is the recoil velocity of the gun ? 7) What is weight ? State the direction in which it acts. Write an expression for it. Is the weight of an object same on the earth and the moon ? Why ? 8) A circular track has a circumference of 1570 m with AB as one of its diameter. A scooterist moves from A to B along the circular path with a uniform speed of 5 m/s. Find the :

(a) distance covered by the scooterist, (b) displacement of the scooterist (Given ∏=3.14), (c) time taken by the scooterist in reaching from A to B. 9) A man throws a ball of mass 0.5 kg vertically upward with a velocity of 25 m/s. Find : (a) the initial momentum of the ball (b) momentum of the ball at the half way mark of the maximum height (given g=10 m/s2) 10) A body thrown in the vertically upward direction rises upto a height „h‟ and comes back to the position of its start. Calculate (a) the total distance travelled by the body and (b) the displacement of the body. Under what condition will the magnitude of the displacement be equal to the distance travelled by an object ? 11) Which is having a higher value of momentum - A bullet of mass 10 g moving with a velocity of 400m/s or a cricket ball of mass 400g thrown with the speed of 90 km/h ?

12)Show that weight of an object on the moon is 1/6 of its weight on the earth. [Given...

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