Our physics problems

Physics problems from 22 sub-categories of physics

difficulty graded (1-10)

GCSE problem (8/10 for gcse)

When a 56 gram tennis ball served at 40 meters per second (approximately 90mph) hits a wall and bounces back without loosing any kinetic energy, (i.e. an elastic coalition). The time of the bounce on the wall is 0.05seconds. What force is exerted on the wall?

1- Initial momentum of ball is 0.056 x 40 = 2.24kg m/s towards the wall.

2- Final momentum of the ball is equal to 0.056 x 40 = 2.24kg m/s away from the wall.

3- Hence the change in momentum is 2.24 - (-) 2.24 = 4.48kg m/s.

4- Force = the change of momentum time

5- Force = 4.48 0.05

6- ANSWER- 89.6N (Newtons)

A level (gravity)- (7/10 for A-level)

Taking the earth to be a uniformed sphere of radius 6400km, and the value of the g at the surface to be (10 ms^-2) calculate the total energy needed to rise a satellite of mass 2000kg to a height of 800km above the ground and to set it into circular orbit at that altitude.

A level/Special-circular motion (11-10 for A-level (special problem))

A child is sitting on a metal tray at the top of a perfect large semi-circle of snow. The wind blows and provides a small push on the child and tray, he progresses down the semi circle. At what angle to the vertical does the child along with the tray fall off?

Nuclear disintegration (8-10 for A-level)

An uranium nucleus (238/92) disintegrates into a thorium nucleus (234/90) and an alpha particle (4/2) calculate

A- The total energy realise in the disintegration.

B- The kinetic energy of the alpha particle, assuming the nucleus of the uranium is at rest before the disintegration.

Give both answers in MeV.

You are given the following information- u = unified atomic mass unit. mass of 238 uranium = 238.12492u. mass of 234 thorium 234.11650u. mass of 4He (alpha particle) 4.00387u. Assume 1u is equivalent to 930 MeV.

Taken from Nelkon & Parker Advanced Level Physics Fifth edition

pg,910 Q,30

A simple pendulum problem (5-10) for A-level

A simple pendulum had a period of 4.2s, when the pendulum is shortened by 1m the new period is 3.7s.

A- From these measurements calculate the acceleration of freefall g and the original length of the pendulum (to 1 d.p.).

B- If the pendulum is taken from the earth to the moon where the acceleration of freefall is g/6, What relative change, if any, occurs in the period T?

Radioactive dating Problem for A-level (7-10)

The isotope of Potassium (Atomic mass 40, Atomic number 19) has a half life of 1.37 billion years, It decays to Argon (Atomic mass 40, Atomic number 18) which is stable. Moon rocks from the sea of tranquillity show that the ratio of these Potassium atoms to Argon atoms is 1/7.

A- Estimate the age of these rocks.

B- Certain other rocks give a value of 1/4 for this ratio by any means of graph or calculations estimate their age (I have chosen calculations)

source.. Nelkon & Parker advanced level physics fifth edition p.g 907 Q.12

Gravity/ Binary star system for A-level (7/10)

Two binary stars, masses 1 x 10^20 kg and 2 x 10^20 kg respectively, rotate about their common centre of mass with an angular velocity w. Assuming that the only force on the star is the mutual gravitational force between them, calculate w. Assume that the distance between the stars is 1 x 10^6 km and that G is 6.7 x 10^-11 N m^2 kg^-2.

source.. Nelkon & Parker advanced level physics fifth edition p.g. 58 Q.9