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Review problems Mechanics Revision. A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal.

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Presentation on theme: "Review problems Mechanics Revision. A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal."— Presentation transcript:

1 Review problems Mechanics Revision

2 A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal. Given that the coefficient of friction between the parcel and the chute is 0.2, and neglecting any other resistances, calculate the acceleration of the parcel as it slides down the chute. Step 1 – Draw your diagram.

3 A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal. Given that the coefficient of friction between the parcel and the chute is 0.2, and neglecting any other resistances, calculate the acceleration of the parcel as it slides down the chute. Step 2 – Look at equations you might need F = ma F = uR

4 A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal. Given that the coefficient of friction between the parcel and the chute is 0.2, and neglecting any other resistances, calculate the acceleration of the parcel as it slides down the chute. Step 4 – Calculate with no friction F = m * a * sin(O) F = 3 * g * sin(40) F = 19.3N

5 A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal. Given that the coefficient of friction between the parcel and the chute is 0.2, and neglecting any other resistances, calculate the acceleration of the parcel as it slides down the chute. Step 5 – Calculate the normal force R = m * g * cos(O) R = 3 * 10 * cos(40) R = 23N

6 A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal. Given that the coefficient of friction between the parcel and the chute is 0.2, and neglecting any other resistances, calculate the acceleration of the parcel as it slides down the chute. Step 6 – Calculate frictional force F = uR F = 0.2 * 23 F = 4.6

7 A parcel of mass 3kg is released from rest at the top of a straight chute which is fixed at a 40 o angle to the horizontal. Given that the coefficient of friction between the parcel and the chute is 0.2, and neglecting any other resistances, calculate the acceleration of the parcel as it slides down the chute. Step 7 – Use Newton’s 2 nd Law 19.3 – 4.6 = 3 * a a = 4.9 m/s 2

8 A log, of mass 80kg, rests on horizontal ground. When a force of magnitude 240N is applied to the log in an upward direction that makes an angle of 20 o with the horizontal then the log is about to move. Model the log as a particle and calculate the coefficient of friction between the log and the ground. Step 1 – Draw your diagram.

9 A log, of mass 80kg, rests on horizontal ground. When a force of magnitude 240N is applied to the log in an upward direction that makes an angle of 20 o with the horizontal then the log is about to move. Model the log as a particle and calculate the coefficient of friction between the log and the ground. Step 1 – Draw your diagram. How to think about this problem at first.

10 A log, of mass 80kg, rests on horizontal ground. When a force of magnitude 240N is applied to the log in an upward direction that makes an angle of 20 o with the horizontal then the log is about to move. Model the log as a particle and calculate the coefficient of friction between the log and the ground. Step 1 – Draw your diagram. Now model it as a particle like the problem asks.

11 A log, of mass 80kg, rests on horizontal ground. When a force of magnitude 240N is applied to the log in an upward direction that makes an angle of 20 o with the horizontal then the log is about to move. Model the log as a particle and calculate the coefficient of friction between the log and the ground. Step 2 – Calculate normal force. R = 800 – 240*sin(20) R = 718N

12 A log, of mass 80kg, rests on horizontal ground. When a force of magnitude 240N is applied to the log in an upward direction that makes an angle of 20 o with the horizontal then the log is about to move. Model the log as a particle and calculate the coefficient of friction between the log and the ground. Step 3 – Calculate friction force. F = 240 * cos(20) F = 225.5N

13 A log, of mass 80kg, rests on horizontal ground. When a force of magnitude 240N is applied to the log in an upward direction that makes an angle of 20 o with the horizontal then the log is about to move. Model the log as a particle and calculate the coefficient of friction between the log and the ground. Step 4 – Solve for coefficient of friction F = uR 225.5 = u * 718 u = 0.314


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