std 9 Science 1st Unit test

Q 1) A) Fill in banks.
1. Deceleration is __________ acceleration.
2. _________ is the rate at which work is done.

B) Say true or false. If false, rewrite the correct statement.
1. When an object is at rest , its initial velocity is zero.

C) Find the odd man out.
Speed, acceleration, velocity, momentum

D) Complete the co-relation.
Potential energy : mgh :: kinetic energy : __________

E) Rewrite the statement by choosing correct alternatives.
a.  1 horsepower = _______ watt.
a) 764       b) 467     c) 746      d) 846

b. The working of rocket depends on Newton's _________ law of motion.
a) first      b) second       c) third      d) none of these

c. The unit of acceleration is  _________
a) m/s       b) m/s square    c) cm/s      d) m square / s

d. Joule is the unit of _______
a) force      b) power     c) work      d) momentum

e. Momentum (P) = _____
a. mv square         b) m square  v         c) mv        d) m v square/r


Q 2 Answer the following.
a) Differentiate between Distance and displacement.
b) Give reason - It is easy to stop a tennis ball as compared to a cricket ball, when both are travelling with the same Velocity.
c) An athlete is running on a circular track. He runs a distance of 500 m in 25s before returning to his original position. what is his average speed and velocity ?
d) If an object has zero momentum, does it have kinetic energy ? explain your answer
e) Ravi applied a force of 10N and moved a book 20cm in the direction of force, how much was work done by Ravi
f) A 50W electric bulb is used for 10 hr. everyday. How much electricity does it consume each day ?

Q 3. solve the following
1. Write Newton's 3 laws of motion.
2. Derive expression for kinetic energy.
3. The velocity of car increases for 36 km / hr to 54 km / hr. How much is the work done if the mass of a car is 1500 kg.

4. derive the formula F = ma
5. What is acceleration ? Write its formula and a note on types of acceleration.
6. A motorcycle starts form rest and moves with uniform acceleration. If it attains the velocity of 20 m/s in 5s. calculate the acceleration and the distance travelled in that time
7. Write the direction of force and displacement in each of the following cases ?
a) Pushing a stalled vehicle b) catching the ball which your friend has thrown towards you
c) Tying a stone to one end of a string and swinging it round and round by the other end of the string.

Q 4. Answer the following
1. To prove when two objects collide, the total momentum before collision is equal to the total momentum after collision.
2. Study the following activity  and answer the question.
 1. take 2 aluminium channels on the floor and hold their upper ends at the same height.
2.Now take balls of the same size and weight and release them form the top end of the channels
 they will roll down and cover the same distance.

Questions
a) At the moment of releasing the balls, which energy do the balls have ?
b) as the balls roll down which energy is converted into which other form of energy ?
c) Why do the balls cover same distance on rolling down ?
d) What is the  form of eventual total energy of the balls ?
e) Which law related to the energy does the above activity demonstrate ?

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