CL-IX-PHYSICS Revision Day-5
Sl.
No Questions
.
1. a) A bullet of mass 30 g is fired with a rifle. The bullet takes 0.05 s to move through
the barrel and leaves with a velocity of 300 m/s. What is the force (in N) exerted on
the bullet by the rifle?
b) A bullet fired from a gun is more dangerous than an air molecule hitting a person,
though both of them have almost the same speed. Why?
c) Impulsive force is large and acts for a short time. Justify with an example.
d) Find the force needed to speed up a car with a rate of 8 m/s², if the mass of the
car is 1200 kg.
2. A cyclist travels ¼ round of a circular track of radius 400m. What is the displacement
and distance travelled by the cyclist?
3. Two electrons are placed at 10 Fermi (femtometre). Calculate the gravitational force
of attraction between them. mass of electron 9.1x10 -31kg and 1 fermi =10-15 m
4. The velocity-time graph for a car is shown in the figure below. Using this figure,
calculate
(a) what type of motion is represented by (i) BD (iii) DE
(b) the acceleration in the last two hours
(c) the total distance travelled by the car from B to D
5. An object is dropped from rest at a height of 100 m and simultaneously another
object is dropped from rest at a height 80 m. What is the difference in their heights
after 2 s if both the objects drop with same accelerations? How does the difference
in heights vary with time?
Sl.
No Questions
.
1. a) A bullet of mass 30 g is fired with a rifle. The bullet takes 0.05 s to move through
the barrel and leaves with a velocity of 300 m/s. What is the force (in N) exerted on
the bullet by the rifle?
b) A bullet fired from a gun is more dangerous than an air molecule hitting a person,
though both of them have almost the same speed. Why?
c) Impulsive force is large and acts for a short time. Justify with an example.
d) Find the force needed to speed up a car with a rate of 8 m/s², if the mass of the
car is 1200 kg.
2. A cyclist travels ¼ round of a circular track of radius 400m. What is the displacement
and distance travelled by the cyclist?
3. Two electrons are placed at 10 Fermi (femtometre). Calculate the gravitational force
of attraction between them. mass of electron 9.1x10 -31kg and 1 fermi =10-15 m
4. The velocity-time graph for a car is shown in the figure below. Using this figure,
calculate
(a) what type of motion is represented by (i) BD (iii) DE
(b) the acceleration in the last two hours
(c) the total distance travelled by the car from B to D
5. An object is dropped from rest at a height of 100 m and simultaneously another
object is dropped from rest at a height 80 m. What is the difference in their heights
after 2 s if both the objects drop with same accelerations? How does the difference
in heights vary with time?
